Trigonometry Calculator — sin, cos, tan & Right Triangles

Use this free trigonometry calculator two ways. Evaluate a ratio — pick sin, cos, tan, csc, sec or cot and enter an angle in degrees or radians. Or solve a right triangle — enter any two sides to get the third side, all three ratios, and the reference angle.

How to use the calculator

1. Choose a mode: evaluate a trig ratio, or solve a right triangle.
2. Enter the angle (with degrees/radians) or the two known sides.
3. Press Calculate to see the result and the steps.

SOH–CAH–TOA

In a right triangle, sin = opposite/hypotenuse, cos = adjacent/hypotenuse, and tan = opposite/adjacent. The calculator uses these definitions (and the Pythagorean theorem for the missing side) and flags undefined cases like tan(90°).

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Frequently asked questions

Does it work in degrees and radians?

Yes — switch the angle mode and the calculator evaluates trig functions in whichever unit you choose. sin(30°) = 0.5.

Can it solve a right triangle?

Yes — enter any two of the opposite, adjacent and hypotenuse, and it finds the third side (Pythagoras) plus the ratios and the reference angle.

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What about undefined values like tan(90°)?

The calculator detects them and shows a clear ‘undefined’ message instead of a wrong number.

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Read the full lesson: learn the method step by step.

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