The value of cos²20° + cos²70° is?

A. $$\sqrt 2 $$

B. 2

C. $$\frac{1}{{\sqrt 2 }}$$

D. 1

Answer: Option D

Solution(By Examveda Team)

$$\eqalign{ & {\text{co}}{{\text{s}}^2}{20^ \circ } + {\text{co}}{{\text{s}}^2}{70^ \circ } \cr & = {\text{co}}{{\text{s}}^2}\left( {{{90}^ \circ } - {{70}^ \circ }} \right) + {\text{co}}{{\text{s}}^2}{70^ \circ } \cr & = {\sin ^2}{70^ \circ } + {\text{co}}{{\text{s}}^2}{70^ \circ } \cr & = 1 \cr} $$