Найти log15 75, если log2 5=a, log2 3=b

log15 75=(log2 75)/(log2 15)=(log2 (3*25)/(log2 (3*5)=(log2 3+log2 5^2)/(log2 3+log2 5)=(log2 3

+2log2 5)/(log2 3+log2 5)=(b+2a)/(b+a)

bc^2=ab^2-ac^2=208^2-80^2=36864

bc=192

tg(a)=bc/ca=192/80=2,4

sin(3pi/7+pi/14)