Question

prove that cos 25π=cosπ​

Answer 1

Answer:

lhs,

cos25π

=cos25×180

=cos 180

=-1

rhs

cosπ

=cos180

=cos-1

therefore lhs=rhs

Answer 2

Answer:

LHS

= cos25π

= cos(4*6π -π)

= cosπ = rhs

since,

cos(2nπ- ∅) = cos∅ , where n is any integer.

hence proved