Question

cos(П+x)=sin П/2

sin5x cos4x - cos5x sin4x=1

cos alfa / 1-sin alfa = 1+sin alfa / cos alfa

Answer 1

1)cos(π+x)=sinπ/2
-cosx=1
cosx=-1
x=π+2πn
2)sin5xcos4x-cos5xsin4x=1
sin(5x-4x)=1
sinx=1
x=π/2+2πn
3)cosa/(1-sina)=(1+sina)/cosa
cos²a=(1-sina)(1+sina)
cos²a=1-sin²a
cos²a=cos²a