Question

Результатом упрощения выражения (sin^2 2x-cos^2 3x)/cos5x является...ПОМОГИТЕ РЕШИТЬ ПОЖАЛУЙСТА

Answer 1

$\frac{ sin^{2}2x - cos^{2}3x}{cos5x}= \frac{ 4sin^{2}xcos^{2}x - (4cos^{3}x-3cosx)^2}{16cos^5x-20cos^3x+5cosx}=$$\frac{ 4sin^{2}xcos^{2}x - 16cos^{6}x+24cos^4x-9cos^2x}{16cos^5x-20cos^3x+5cosx}$ = $\frac{cosx( 4sin^{2}xcosx - 16cos^{5}x+24cos^3x-9cosx)}{cosx(16cos^4x-20cos^2x+5)}$=$\frac{4cosx( 1-cos^{2}x) - 16cos^{5}x+24cos^3x-9cosx}{16cos^4x-20cos^2x+5}$=$\frac{4cosx-4cos^{3}x-16cos^{5}x+24cos^3x-9cosx}{16cos^4x-20cos^2x+5}=\frac{20cos^{3}x-16cos^{5}x-5cosx}{16cos^4x-20cos^2x+5}$=$\frac{-cosx(16cos^{4}x-20cos^{2}x+5)}{16cos^4x-20cos^2x+5}=-cosx$