Question

Prove each of the following:
(2) cos 90° = 1 - 2 sin2 45º = 2 cos
2​

Answer 1

Step-by-step explanation:

cos 90=0

sin 45=1/√2

cos 45=1/√2

taking LHS: cos 90=0

taking RHS: 1-2 sin2 45

=1-2(1/√2)^2

=1-2(1/2)

=1-1

=0

now taking RHS:2 cos^2 45-1

=1-2(1/√2)^2

=1-2(1/2)

=1-1

=0

... LHS=RHS

...Hence proved