Question

Trygonometria - Rozwiąż równanie
2cos^2 + √2cos - 2 = 0

Answer 1

T=cosx, t∈<-1;1>
2t²+√2t-2=0
Δ=2+16=18
√Δ=3√2
t=(-√2 +3√2)/4 = (√2)/2 ∈<-1;1>    lub     t=(-√2 - 3√2)/4 = √2∉<-1;1>
cosx=(√2)/2
x=π/4 + 2kπ ∧ x=3π/4 +2kπ, k∈C