Question

find the value of cos15°.?

Answer 1

Heya,

cos^2 15°=1+cos30°/2(we can write )

=1+√3/2/2

=2+√3/4

=multiply by 2 in numerator or denominator

then it become

=【√3+1/2√2】^2

cos^2=+-√3+1/2√2

hope it help you

@rajukumar.

Answer 2

cos (60 -45) = cos60 . cos45 + sin 60 . sin 45
= (1/2)×(1/root(2)) + root (3)/2 × 1/root(2)
=(1+root(3))/2root(2)
further u can rationalise it