Question

вычислите sin2a, cos2a и tg2a, если cosa=3/5 и 0<a<n/2

Answer 1

1)sina^2a=1-cos^2a=1-9/25=16/25
sina=4/5
sin2a=2sinacosa=2*4/5*3/5=24/25
cos2a=cos^2a-sin^2a=9/25-16/25=-7/25
tg2a=sin2a/cos2a=24/25*(-25/7)=-24/7
2) sin^2a=1
sina=1
sin2a=2sinacosa=2*1*0=0
cos2a=cos^2a-sin^2a=0-1=-1
tg2a=sin2a/cos2a=0/-1=0