Wiedząc że tgL =2 oblicz wartość wyrażenia sin²L - 2 cos²L

[latex] analpha=2[/latex] [latex]cfrac{sinalpha}{cosalpha}=2[/latex] [latex]sinalpha=2cosalpha[/latex] [latex]sin^2alpha=4cos^2alpha[/latex] [latex]sin^2alpha+cos^2alpha=1[/latex] [latex]4cos^2alpha+cos^2alpha=1[/latex] [latex]5cos^2alpha=1[/latex] [latex]cos^2alpha=cfrac{1}{5}[/latex] [latex]sin^2alpha-2cos^2alpha=4cos^2alpha-2cos^2alpha=2cos^2alpha=2cdotcfrac{1}{5}=cfrac{2}{5}[/latex]