Question

3cos7pi/4+2sin3pi/4-sin(-9pi/4)+7cos13pi/2
Помогите пожалуйста решить, очень срочно!!!!!

Answer 1

cos7π/3=cos(2π+π/3)=cosπ/3=1/2
sin3π/4=sin(π-π/4)=sinπ/4=√2/2
sin(-9π/4)=-sin9π/4=-sin(2π+π/4)=-sinπ/4=-√2/2
cos13π/2=cos(6π+π/2)=cosπ/2=0
3×1/2+2×√2/2-(-√2/2)+7×0=3/2+√2+√2/2=(3+3√2)/2