Question

Mă puteți ajuta? vă rog frumos

Answer 1

Răspuns:

Explicație pas cu pas:

$\texttt{Folosim urmatoarele formule:}\\\boxed{\cos(90\textdegree-a)=\sin a}\\\boxed{\cos(180\textdegree-a)=-\cos a}\\\texttt{Revenim la exercitiu:}\\\cos^210\textdegree+\cos^2100\textdegree=\cos^2(90\textdegree-80\textdegree)+\cos^2(180\textdegree-80\textdegree)=\\=\sin^280\textdegree+(-\cos80\textdegree)^2=\sin^280\textdegree+\cos^280\textdegree=\boxed{1}$