Question

4(cos20-sin20)/ √2sin25

 

Answer 1

$cos(90-70)-sin20=sin70-sin20=2sin frac{70-20}{2} cos frac{70+20}{2}$$=2sin25cos45=2* frac{ sqrt{2} }{2} sin25= sqrt{2} sin25$
$4 frac{ sqrt{2}sin25}{ sqrt{2}sin25 } = 4$