Question

$\sin {79}^{\circ }\cos {11}^{\circ }+\cos {79}^{\circ }\sin {11}^{\circ }=$

• A. $\frac{1}{\sqrt{2}}$
• B. $\frac{1}{2}$
• C. $0$
• D. $1$

Answer 1

The correct option is D $1$

Given

$\sin {79}^o\cos {11}^o+\cos 79\sin {11}^o$

$=\sin {79}^o\cos \left({90}^o-{79}^o\right)+\cos {79}^o\sin \left({90}^o-{79}^o\right)$

$=\sin {79}^o\sin {79}^o+\cos {79}^o\cos {79}^o$

$={\sin }^2{79}^o+{\cos }^2{79}^o$ as we know $={\sin }^2\theta +{\cos }^2\theta =1$

$=1$