Question

Question 3 (ii)
Evaluate:
(ii) $sin{25}^{\circ }cos{65}^{\circ }+cos{25}^{\circ }sin{65}^{\circ }$

Answer 1

(ii) $sin{25}^{\circ }cos{65}^{\circ }+cos{25}^{\circ }sin{65}^{\circ }$
$=sin({90}^{\circ }-{65}^{\circ })cos{65}^{\circ }+cos({90}^{\circ }-{65}^{\circ })sin{65}^{\circ }$
$=cos{65}^{\circ }cos{65}^{\circ }+sin{65}^{\circ }sin{65}^{\circ }$
$=co{s}^2{65}^{\circ }+si{n}^2{65}^{\circ }=1$