Вычеслить cos 3п/8 !!!!!!!!!!!!!!!!

Question

Вычеслить cos 3п/8 !!!!!!!!!!!!!!!!

Answer 1

Решение 
cos(3π/8)=cos(π/2-π/8)=sin(π/8)=√((1-cos(π/4))/2)=√(½-√2/4)=√(2-√2)/2=0,38