Free Interactive Trigonometry Calculator

Trig Buddy is a free, visual trigonometry calculator built around the unit circle. Drag the point around the circle, or scrub along the wave, and watch sine, cosine, tangent, cosecant, secant and cotangent update as you go, with exact values like √3/2 wherever they exist. Switch between the circle, the wave, or both side by side to see how a turning point traces out a sine curve. No sign-up, no ads, works on desktop and mobile.

What you can calculate

  • All six trig functions of any angle, with exact values at every multiple of 15° (π/12).
  • Degrees, radians (as multiples of π like 5π/6), and degrees-minutes-seconds.
  • Quadrant, reference angle and coterminal angles, and which functions are positive there.
  • Inverse trig: solve sin θ = v (or cos, tan, csc, sec, cot) for the principal value, every solution in one turn, and the general solution.
  • Right triangles with SOH-CAH-TOA: set any two of the angle, opposite, adjacent and hypotenuse.
  • Sinusoids y = A·sin(B(x − C)) + D: amplitude, period, phase shift, vertical shift, range and key points, graphed over the original wave.

Who it's for

Students in trigonometry, precalculus and physics checking homework or building intuition, teachers demonstrating the unit circle live, and anyone who works with angles, slopes, waves or oscillations: carpenters and roofers finding rise, run and pitch, electricians and audio folks reasoning about phase, and engineers who want a quick answer without installing software.

Frequently asked questions

How do I find the exact value of sin, cos or tan?

Type the angle or drag to it. At multiples of 15° (π/12) Trig Buddy shows the exact form, such as √3/2 or 2 − √3, next to the decimal. Other angles show decimals to your chosen precision.

How do I solve an equation like sin x = 0.5?

Open Inverse, pick the function and enter the value. Fractions and square roots work, like 1/2 or √3/2. You get the principal value, every solution in one full turn, and the general solution with k any integer.

Can it solve a right triangle?

Yes. In Triangle mode, set any two of the angle, opposite, adjacent and hypotenuse (at least one must be a side) and the rest is solved, along with the other angle, the area and the perimeter.

How do I find the amplitude, period and phase shift of a sine wave?

In Sinusoid mode, enter A, B, C and D for y = A·sin(B(x − C)) + D, or pick the cosine version. Trig Buddy lists the amplitude, period, phase shift, vertical shift, range and the five key points of one period, and draws the wave over the original.

Does it work in radians?

Yes. Switch DEG or RAD at the top. You can always type π for radians (5π/6) or add ° for degrees, whichever unit is selected.

Is Trig Buddy free?

Yes. It's completely free, there are no ads, and it runs entirely in your browser.

Trig Buddy · part of the Triangle Buddy family of free math tools · also try Fraction Buddy.