Question

f(x) = - 4 cos ( π / 2 - x)+ 2.cos(x), o valor de f(-7π/4)
vale?​

Answer 1

Resposta:

Explicação passo-a-passo:

temos:

f(x) = -4cos (π/2 - x ) + 2cos (x)

f(x) = 2cos (x) - 4 cos (π/2 - x)

f(-7π/4) = 2cos (-7π/4) - 4cos π/2 - (-7π/4)

f(-7π/4) = 2cos (-7π/4) -4cos (π/2 + 7π/4 )

f(-7π/4) =2cos (-7π/4) -4cos (2π/4 +7π/4 )

f(-7π/4) =2cos (-7π/4) -4cos (9π/4)

f(-7π/4) = 2 * √2/2 - 4 * √2/2

f(-7π/4) = √2 - 2√2

f(-7π/4) = -√2