There are 2 methods, at least to prove the
identity.
One method is to manage only the left side,
changing the value 1 into sin 90. Then, we'll transform teh sum into a
product.
The other method is to manage only the right side
and to expand the cosine of the difference.
cos (90 - x) =
cos 90*cos x + sin 90*sin x
cos 90 = 0 and sin 90 =
1
cos (90 - x) = 0*cos x + 1*sin
x
cos (90 - x) = sin x
cot 45
= 1
We'll substitute the terms from the right side and
we'll get:
1 + sin x = sin x +
1
The addition is commutative and LHS =
RHS=> the given identity,1+sinx=cos(90-x)-cot45, is
true.
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