Question

(2sin x + cos x)^2 + (sin xb+ 2cos x)^2 - 4sin2x = 5

Answer 1

utilizam formulele $(a+b)^2=a^2+2ab+b^2$; $sin^2x+cos^2x=1$;
$sin2x=2sinx*cosx$
$4 cos^{2}x+4sinxcosx+ cos^{2}x+ sin^{2}x+4sinxcosx+4 cos^{2}x-8sinxcosx \\ = 5 cos^{2}x+5 sin^{2}x+8sinxcosx-8sinxcosx=5(cos^2x +sin^2x)=5$
ceea ce trebuia de aratat