вычислить.sin a (5 cos+2)/(10 cos a + 4)* cos a?если tg a =5

1. а)(sina+cosa)/(2sina-cosa)= [cosa*(tga+1)] / [cosa*(2tga-1)] = (tga+1)/(2tga-1)=(5/4+1) / (2*5/4-1)= (9/4)/(6/4)=9/6=1,5 2) а)1 - sin2 a + ctg2 a * sin2 a= cos2a+cos2a / sin2a= cos2a+cos2a=2*cos2a