Hey !

2sin ^2( theta)= 1- cos (2 theta)

let theta=15

then,

2sin ^2(15)= 1- cos (2 x 15)

sin ^2(15)= (1- cos (30) )/2

= (1- (root(3)/2))/2

sin (15)    =root ( (1- ( root(3)/2) ) / 2 )

= ( root(6) - root(2) )/4

= 0.25

.

This is a very easy question. You just need to put theta value on both side. Put theta=15 and solve the value of sin

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• Write each and every formula of a chapter in a sheet of paper and put it up on the front wall of your study place.
• Solve the questions by seeing the formulas. You will remember the formulas better through this technique.
• Use the calculator whenever you need. It will save time.

Hello,

I found: sin(15°)=0.258

Explanation:

Using the Formula given in question:
sin2(x)=[1−cos(2x)] /2

with x=15° and 2x=30°

you get:

sin2(15°)=[1−cos(30°)]/2

knowing that: cos(30°)=√3/2 :

sin2(15°)=[1−√3 / 2]/2
sin2(15°)=(2−√3) 4=0.067

So:
sin(15°)=±√0.067=±0.258
We choose the positive one.

Hope you will understand :)