Posted by Maddie on .
If tan y = 4/3 and y is in Q I'VE find cos 2y

trig 
Steve,
well, you know that
siny = 3/5
cos2y = 1  2sin^2 y
or, you know that
tan 2y = 2tany/(1tan^2 y)
and sec^2 2y = 1 + tan^2 2y
good way to check your answer.