Ответ:

√18(1 — 2[tex]Sin^{2}(5Pi/8)[/tex])=3√2Cos(5Pi/4) = 3√2(-√2/2) = -3

 

1) 1 — 2sin^2(x)= cos 2x

2) 5Pi/4 = Pi + Pi/4, Cos(5Pi/4)=-cos(Pi/4)