Conic Section Equation
Mathematics · FE Reference Handbook section
Handbook notes for this section
Definitions and conditions exactly as the handbook states them.
- The general form of the conic section equation is
- where not both A and C are zero.
- is the normal form of the conic section equation, if that conic section has a principal axis parallel to a coordinate axis.
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
A mathematics problem uses Parabola vertex form. Given coefficient (a) = 2.0000; x-value (x) = 3.0000; vertex x (h) = 0.0000; vertex y (k) = -1.0000, determine the y-value (y).
Given
Find
y-value (y)
Start with the thinking
- The governing relation printed in this handbook section is Parabola vertex form.
- Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Mathematics items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that y stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning y = 17.0000 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 34.0000 — kept a factor of two that cancels in the correct rearrangement.
- 8.5000 — dropped that same factor in the other direction.
- 18.7000 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mathematics → Conic Section Equation
an elliptical culvert opening Given semi-major axis (a) = 2.3000 m; semi-minor axis (b) = 1.8000 m, determine the area (A) in m^2.
Given
Find
area (A), in m^2
Start with the thinking
- The governing relation printed in this handbook section is Area of an ellipse.
- Everything except A is given, so isolate A symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A survey monument plate is machined as an ellipse.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for A:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
A = 13.0062\ \text{m^2}Step 6 — Check: returning A = 13.0062 m^2 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 26.0124 — kept a factor of two that cancels in the correct rearrangement.
- 6.5031 — dropped that same factor in the other direction.
- 14.3068 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Ellipse)
Eccentricity measures how far the conic departs from a circle. Given semi-major axis (a) = 6.8000 m; semi-minor axis (b) = 4.4000 m, determine the eccentricity (e).
Given
Find
eccentricity (e)
Start with the thinking
- The governing relation printed in this handbook section is Eccentricity of an ellipse.
- Everything except e is given, so isolate e symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Eccentricity measures how far the conic departs from a circle.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for e:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning e = 0.7624 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.5249 — kept a factor of two that cancels in the correct rearrangement.
- 0.3812 — dropped that same factor in the other direction.
- 0.8387 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Ellipse)
A vertical curve profile is modeled as a parabola. Given curvature coefficient (a) = 0.1000 1/m; station offset (x) = 2.4000 m; vertex station (h) = 0.4000 m; vertex elevation (k) = 13.3000 m, determine the elevation (y) in m.
Given
Find
elevation (y), in m
Start with the thinking
- The governing relation printed in this handbook section is Parabola (vertex form).
- Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A vertical curve profile is modeled as a parabola.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for y:
Step 3 — List the givens: curvature coefficient (a) = 0.1000 1/m, station offset (x) = 2.4000 m, vertex station (h) = 0.4000 m, vertex elevation (k) = 13.3000 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning y = 13.7000 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 27.4000 — kept a factor of two that cancels in the correct rearrangement.
- 6.8500 — dropped that same factor in the other direction.
- 15.0700 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Parabola)
A student evaluates a conic section equation at a given x-value. Given quadratic coefficient (a) = 2.9000; linear coefficient (b) = -0.5000; constant term (c) = 0.1000; x-value (x) = 0.9000, determine the y-value (y).
Given
Find
y-value (y)
Start with the thinking
- The governing relation printed in this handbook section is Conic section equation — parabola form.
- Everything except y is given, so isolate y symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The general conic section equation for a parabola relates its coefficients to a point on the curve.
Figure 5 — schematic for Conic section equation — parabola form — solve for y-value — Conic Section Equation (5)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for y:
Step 3 — List the givens: quadratic coefficient (a) = 2.9000, linear coefficient (b) = -0.5000, constant term (c) = 0.1000, x-value (x) = 0.9000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning y = 1.9990 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.9980 — kept a factor of two that cancels in the correct rearrangement.
- 0.9995 — dropped that same factor in the other direction.
- 2.1989 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Section Equation
A mathematics problem uses Parabola vertex form. Given x-value (x) = 5.0000; vertex x (h) = 1.0000; vertex y (k) = 5.0000; y-value (y) = -36.0000, determine the coefficient (a).
Given
Find
coefficient (a)
Start with the thinking
- The governing relation printed in this handbook section is Parabola vertex form.
- Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Mathematics items reward recognising the unknown before touching a calculator.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange the relation so that a stands alone on the left-hand side.
Step 3
Step 4 — Substitute the given values into the rearranged relation.
Step 5 — Evaluate:
Step 6 — Check: returning a = -2.5625 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -5.1250 — kept a factor of two that cancels in the correct rearrangement.
- -1.2813 — dropped that same factor in the other direction.
- -2.8188 — rounded an intermediate value before the final step.
Reference: FE Reference Handbook — Mathematics → Conic Section Equation
an elliptical bearing plate Given area (A) = 7.2000 m^2; semi-minor axis (b) = 1.5000 m, determine the semi-major axis (a) in m.
Given
Find
semi-major axis (a), in m
Start with the thinking
- The governing relation printed in this handbook section is Area of an ellipse.
- Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A survey monument plate is machined as an ellipse.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for a:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning a = 1.5279 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.0558 — kept a factor of two that cancels in the correct rearrangement.
- 0.7639 — dropped that same factor in the other direction.
- 1.6807 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Ellipse)
Eccentricity measures how far the conic departs from a circle. Given eccentricity (e) = 0.8000; semi-major axis (a) = 2.6000 m, determine the semi-minor axis (b) in m.
Given
Find
semi-minor axis (b), in m
Start with the thinking
- The governing relation printed in this handbook section is Eccentricity of an ellipse.
- Everything except b is given, so isolate b symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Eccentricity measures how far the conic departs from a circle.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for b:
Step 3
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning b = 1.5600 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 3.1200 — kept a factor of two that cancels in the correct rearrangement.
- 0.7800 — dropped that same factor in the other direction.
- 1.7160 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Ellipse)
A vertical curve profile is modeled as a parabola. Given elevation (y) = 11.2000 m; station offset (x) = 4.6000 m; vertex station (h) = 1.8000 m; vertex elevation (k) = 3.8000 m, determine the curvature coefficient (a) in 1/m.
Given
Find
curvature coefficient (a), in 1/m
Start with the thinking
- The governing relation printed in this handbook section is Parabola (vertex form).
- Everything except a is given, so isolate a symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- A vertical curve profile is modeled as a parabola.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for a:
Step 3 — List the givens: elevation (y) = 11.2000 m, station offset (x) = 4.6000 m, vertex station (h) = 1.8000 m, vertex elevation (k) = 3.8000 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning a = 0.9439 1/m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 1.8878 — kept a factor of two that cancels in the correct rearrangement.
- 0.4719 — dropped that same factor in the other direction.
- 1.0383 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Sections (Parabola)
A designer fits a conic section equation to a vertical curve. Given quadratic coefficient (a) = 3.0000; linear coefficient (b) = -3.4000; x-value (x) = -1.9000; y-value (y) = -10.1000, determine the constant term (c).
Given
Find
constant term (c)
Start with the thinking
- The governing relation printed in this handbook section is Conic section equation — parabola form.
- Everything except c is given, so isolate c symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- The general conic section equation for a parabola relates its coefficients to a point on the curve.
Figure 10 — schematic for Conic section equation — parabola form — solve for constant term — Conic Section Equation (10)
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for c:
Step 3 — List the givens: quadratic coefficient (a) = 3.0000, linear coefficient (b) = -3.4000, x-value (x) = -1.9000, y-value (y) = -10.1000.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning c = -27.3900 to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- -54.7800 — kept a factor of two that cancels in the correct rearrangement.
- -13.6950 — dropped that same factor in the other direction.
- -30.1290 — rounded an intermediate value before the final step.
Reference: FE Handbook — Conic Section Equation