The value of cos220° + cos270° = ?

Answer: Option B

$$\begin{array}{rl}& ={\cos }^{2}20^{\circ }+{\cos }^{2}70^{\circ }\\ & ={\cos }^2\left({90}^{\circ }-{70}^{\circ }\right)+{\cos }^{2}70^{\circ }\\ & =1\end{array}$$