Suppose \sin (u)=\frac{3}{5} and cos (u) is negative. Then \cos (u)= \tan (u)= \sin (-u)= \cos (-u)= \tan (-u)= \sin (u+\pi)= \cos (u+\pi)= \tan (u+x)= \sin \left(u+\frac{\lambda}{2}\right)= \cos \left(u+\frac{\pi}{2}\right)= \tan

\left(u+\frac{\pi}{2}\right)=