Trigonify

Basics

SOHCAHTOA: the sine, cosine and tangent ratios

sin⁡θ=opphypcos⁡θ=adjhyptan⁡θ=oppadj\sin\theta = \dfrac{\text{opp}}{\text{hyp}}\quad \cos\theta = \dfrac{\text{adj}}{\text{hyp}}\quad \tan\theta = \dfrac{\text{opp}}{\text{adj}}

SOHCAHTOA is the mnemonic for the three ratios in a right triangle: sine is opposite over hypotenuse, cosine is adjacent over hypotenuse, tangent is opposite over adjacent. Everything else in trigonometry is built on these three. Use it whenever a problem gives you a right angle and any two of a side, an angle, or the hypotenuse.

right trianglebasic

Related Basics identities

Degrees ↔ radiansArc lengthSector area

Practise it

Reading a formula is not the same as recalling it under time pressure. The workspace drills Basics questions in the quiz, and the triangle solver shows a worked solution for any triangle you type in.

Practise BasicsOpen the triangle solver

Or browse all 45 identities in the full reference, or read the trigonometry guides for the method behind them.