How do I convert between degrees and radians?

1° = π/180 rad and 1 rad = 180/π ≈ 57.2958°. Switch the unit button and both values are shown together.

Why is tan 90° undefined?

Because cos 90° = 0 and tan = sin / cos, so the denominator vanishes. tan is undefined at every 90°+k·180°.

Why does the inverse function return only one angle?

Inverse functions return principal values: asin in [−90°, 90°], acos in [0°, 180°], atan in (−90°, 90°). Other solutions follow by adding the period.

What is a reference angle?

The acute angle between the terminal side and the x-axis. It determines the magnitude of the trigonometric ratios, while the quadrant determines the sign.

Can I see the graphs of these functions?

Yes. Click “Plot the trig functions” under the results to open sin, cos and tan together in the grapher, with the x-axis labelled in multiples of π so the period and symmetry are easy to read.

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📐Trigonometry Calculator - sin, cos, tan, Inverse Functions and DMS

Enter an angle in degrees or radians to get all six trigonometric functions, along with the angle in radians, gradians and turns, its quadrant and reference angle. You can also work backwards from a value to an angle, or convert between degrees–minutes–seconds and decimal degrees.

Free · No sign-up · Runs in your browserLast updated: 2026-10-26

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How to use Trigonometry

1Choose function values, inverse functions or DMS conversion
2Enter the angle and pick degrees or radians, or enter the function value
3Read the results; the special-angle buttons fill in 30°, 45°, 60° and more

FAQ

How do I convert between degrees and radians?: 1° = π/180 rad and 1 rad = 180/π ≈ 57.2958°. Switch the unit button and both values are shown together.
Why is tan 90° undefined?: Because cos 90° = 0 and tan = sin / cos, so the denominator vanishes. tan is undefined at every 90°+k·180°.
Why does the inverse function return only one angle?: Inverse functions return principal values: asin in [−90°, 90°], acos in [0°, 180°], atan in (−90°, 90°). Other solutions follow by adding the period.
What is a reference angle?: The acute angle between the terminal side and the x-axis. It determines the magnitude of the trigonometric ratios, while the quadrant determines the sign.
Can I see the graphs of these functions?: Yes. Click “Plot the trig functions” under the results to open sin, cos and tan together in the grapher, with the x-axis labelled in multiples of π so the period and symmetry are easy to read.