Question

tana=3(1)sinacosa?(2) sin2a-cos2a?

Answer 1

(1)∵tana=sina/cosa=3,sin^2a+cos^2a=1 ∴sina=3√10/10,cosa=√10/10或sina= -3√10/10,cosa= -√10/10 ∴sinacosa=(±3√10/10)*(±√10/10)=3/10 (2)sin2a-cos2a=2sinacosa-(2cos^2a-1)=2*3/10-(2*1/10-1)=3/5-(-4/5)=3/5+4/5=7/5