Question

Oblicz:

Answer 1

A)
x/4-π/5=(3/4)π+kπ
x/4=19/20)π +kπ
x=(19/5)π+4kπ, k∈C

b)
cosx(cosx-sin3x)=0
cosx=0⇔x=π/2+kπ, k∈C
lub
cosx-sin3x=0⇔sin(π/2-x)-sin3x=0⇔2sin(π/4-2x)cos(π/4+x)=0⇔
-sin(-π/4+2x)=0  ∨  cos(π/4+x)=0
2x-π/4=kπ         ∨  x+π/4=π/2+kπ
2x=π/4+kπ       ∨  x=π/4+kπ
x=π/8 +(kπ)/2           k∈C