11, 0
f(n)=sin(30n)
∴Fórmula original = sin 3sin 9sin 15sin 210 +sen 27sen 330 = 0.
12, 17/9
Fórmula original = (1/2)-(1/2)×(-1)-(1/3)×(1/3) -(-1)+(-√)
=(1/2)+(1/2)-(1/9)+1
=2-(1/ 9)
=17/9
13. f(x)=sen2x-cosx
∫f(x) es una función impar y x >: 0 , f(x)=sen2x+cosx.
∴f(-x)=-f(x)=-sin2x-cosx=sin(-2x)-cos(-x)
∴x<0,f( x)=sin2x-cosx.
14. -√3/2
(cosa-sina)? = 1-2 Sina cosa = 1-2×(1/8)= 3/4
∵π/4 & lt; a & ltπ/2
∴·Cosa & ltSina.com
∴cosa-sina=-√(cosa-sina)? =-√(3/4)=-√3/2