# If sin x= 4/5, how do you find cos x?

cosx= $\frac{3}{5}$
Use Trignometrical identity cosx = $\sqrt{1 - {\sin}^{2} x}$
cos x = $\sqrt{1 - \frac{16}{25}}$ =$\sqrt{\frac{9}{25}}$ = $\frac{3}{5}$ to be the value in the first quadranr.