Question

${\sin }^2{20}^{\circ }+{\sin }^2{70}^{\circ }=$?

• A. $0$
• B. $1$
• C. $2$
• D. $3$

Answer 1

The correct option is B $1$

${\sin }^2{20}^{\circ }={\cos }^2({90}^{\circ }-{20}^{\circ })={\cos }^2{70}^{\circ }$

Substituting ${\sin }^2{20}^{\circ }={\cos }^2{70}^{\circ }$

${\sin }^2{20}^o+{\sin }^2{70}^o={\cos }^2{70}^{\circ }+{\sin }^2{70}^{\circ }=1$ $[\because {\sin }^2\theta +{\cos }^2\theta =1]$