Answer:
see explanation
Step-by-step explanation:
Using the trigonometric identity
sin²x + cos²x = 1 , then
sin²x = 1 - cos²x and cos²x = 1 - sin²x
Consider the left side
← expand numerator/denominator using FOIL
=
=
=
=
= cot²A = right side , thus proven
the sine function is a many-to-one function and therefore has no inverse function.
However if the domain is restricted to -90° ≤ x ≤ 90°
Then the function is one-to-one for this domain
Thus, x is defined as the angle such that - π/2 ≤ x ≤ π/2
5π/6 is therefore outwith the domain
