Question

${\cos }^2{47}^{\circ }+{\cos }^2{43}^{\circ }=$

• A. $0$
• B. $1$
• C. $2$
• D. $3$

Answer 1

The correct option is B $1$

We know $\sin \left({90}^o-\theta \right)=\cos \theta$

We know ${\sin }^2\theta +{\cos }^2\theta =1$

To find

${\cos }^2{47}^o+{\cos }^2{43}^o$

${\cos }^2{47}^o={\sin }^2\left({90}^o-{47}^o\right)={\sin }^2\mathring{43}$

Substituting ${\cos }^2{47}^o$ by ${\sin }^2{43}^o$

${\sin }^2{43}^o+{\cos }^2{43}^o=1$