Max and Min on an Ellipse Calculator

Calculate maximum and minimum points with rotated axes. See formulas, steps, exports, and example results. Use clean inputs for accurate boundary decisions every time.

Calculator Inputs

Formula Used

The rotated ellipse is written with local coordinates u and v:

u² / a² + v² / b² = 1

The original coordinates are:

x = h + u cosθ - v sinθ

y = k + u sinθ + v cosθ

The linear objective is:

F(x, y) = Ax + By + C

Convert the objective direction into local axes:

alpha = A cosθ + B sinθ

beta = -A sinθ + B cosθ

The support radius is:

R = √((a alpha)² + (b beta)²)

So the maximum and minimum values are:

Fmax = Ah + Bk + C + R

Fmin = Ah + Bk + C - R

How to Use This Calculator

Enter the ellipse center as h and k. Add positive semi axis values a and b.

Enter the rotation angle in degrees. Use zero for an unrotated ellipse.

Enter A, B, and C for the objective expression F(x, y) = Ax + By + C.

Press Calculate. The result appears below the header and above the form.

Use Download CSV for spreadsheet records. Use Download PDF for a printable result summary.

Example Data Table

h k a b θ A B C Purpose
0 0 5 3 0 2 1 0 Basic unrotated ellipse
1 -2 6 4 30 3 -1 5 Rotated shifted ellipse
-3 2 8 2 45 -2 4 1 Directional boundary test

Practical Guide

Why Ellipse Extremes Matter

An ellipse often describes a limited path. It may show motion, reach, tolerance, stress, or design space. Many tasks ask for the largest or smallest value along that boundary. The value may be height, cost, score, force, or distance along a chosen direction. This calculator handles that question with a direct analytical method. It avoids slow trial guesses. It also returns the point where each extreme occurs.

What The Inputs Mean

The center values move the ellipse on the coordinate plane. The two semi axes set its horizontal and vertical scale before rotation. The rotation angle turns the local ellipse axes around the center. The objective coefficients define the value being tested. They build a linear expression. That expression is evaluated only on the ellipse boundary. A constant term shifts both answers equally. It does not change the two boundary points.

How The Method Works

The formula changes the objective into local ellipse coordinates. Then it uses the support function of an ellipse. This gives the strongest possible projection in any direction. The maximum is the center value plus the support radius. The minimum is the center value minus the same radius. The local extreme point is then rotated back to the original coordinate system. The method is exact for linear objectives. It also works with rotated ellipses.

Reading The Results

A higher maximum means the chosen direction reaches farther along the ellipse. A lower minimum means the opposite direction reaches farther back. If both direction coefficients are zero, every boundary point gives the same value. The result will be constant. In that case, no unique maximum point exists. The table below the form gives sample cases. Use it to compare expected results with your entries.

Good Use Cases

Use this tool for geometry homework, modeling, optimization checks, and engineering sketches. It is helpful when a design must stay inside an elliptical limit. It is also useful when a score depends on two linked variables. Always enter positive semi axes. Use degrees for rotation. Review the displayed steps before exporting. Save the CSV for spreadsheets. Save the PDF for reports, notes, or class records. Keep units consistent throughout each saved calculation and shared file.

FAQs

1. What does this calculator maximize?

It maximizes or minimizes a linear expression, F(x, y) = Ax + By + C, along the boundary of an ellipse.

2. Can I use a rotated ellipse?

Yes. Enter the rotation angle in degrees. The calculator converts the objective into local ellipse coordinates before solving.

3. What happens if A and B are zero?

The expression becomes constant. Every boundary point gives the same value, so no unique extreme point exists.

4. Must a and b be positive?

Yes. Both semi axis values must be positive because they describe ellipse size along local coordinate directions.

5. Does C change the extreme points?

No. C only shifts the maximum and minimum values. The locations of the points stay unchanged.

6. Is this method numerical or exact?

It uses an analytical support formula. Results are direct, except for normal decimal rounding in display output.

7. Can I export the result?

Yes. Use the CSV button for spreadsheet data. Use the PDF button for a printable result summary.

8. Can this solve non-linear objectives?

No. This version is designed for linear objectives only. Non-linear objectives need different methods and checks.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.