Question

The value of cos square 45 - sin square 15

Answer 1

Answer:

cos²45 - sin²15

sin(45-30) =sin15

By using sin(A -B) = sinAcosB-sinBcosB

=sin45cos30-sin30cos45

= 1/√2. √3/2- 1/2.1/√2

√3/√2.2 - 1/2√2

we get = √3-1/2√2

Now put the value of sin 15

we get

cos²40- sin²15

(1/√2)²- (√3-1/2√2)2

=2-2√3/8