calculate cos(x) given tan(x)=8/15

[math_celebrity]

calculate cos(x) given tan(x)=8/15

tan(x) = sin(x)/cos(x)
sin(x)/cos(x) = 8/15

Cross multiply:
15sin(x) = 8cos(x)

Divide each side by 8
cos(x) = 15sin(x)/8