A.4 Trigonometry

\[\sin\theta=\frac{\text{opposite}}{\text{hypotenuse}},\quad \cos\theta=\frac{\text{adjacent}}{\text{hypotenuse}},\quad \tan\theta=\frac{\text{opposite}}{\text{adjacent}}.\]

\[180^\circ=\pi\ \text{radians},\qquad a^2+b^2=c^2.\]

\[\sin^2\theta+\cos^2\theta=1,\] \[\sin(s+t)=\sin s\cos t+\cos s\sin t,\] \[\cos(s+t)=\cos s\cos t-\sin s\sin t.\]