Question

Please prove it for me​

Answer 1

see explanation

Explanation:

Using the trigonometric identity

tanx =
`(1)/(cotx)`

Consider the left side

`(cotA-1)/(cotA+1)` ← divide terms on numerator/denominator by cotA

=
`((cotA)/(cotA)-(1)/(cotA) )/((cotA)/(cotA)+(1)/(cotA) )`

=
`(1-tanA)/(1+tanA)`

= right side , thus proven