Trigonometry connects the angles and sides of triangles, and includes Pythagoras' theorem.
Right-angled triangle
$\sin\theta=\dfrac{O}{H}$ · $\cos\theta=\dfrac{A}{H}$ · $\tan\theta=\dfrac{O}{A}$ · $a^2+b^2=c^2$
Example: with opposite 3 and adjacent 4, $\tan\theta = 0.75$ and the hypotenuse is $\sqrt{3^2+4^2}=5$.
Remember
- SOH-CAH-TOA.
- Pythagoras: $a^2+b^2=c^2$ ($c$ = hypotenuse).