Question

v) 2 sin 105º. sin15°
= ?
​

Answer 1

Answer:

Given that:-2sin105°. Sin15°

We know that 2sinA.sinB=cos(a-b)-cos(a+b)

So, A=105°,B=15°

cos(105-15)°-cos(105+15)°

= cos90°-cos120°

= 0-cos(90+30)° (cos90°=0)

= sin30°

= 1/2 ans. ( sin30°=1/2)