(Q16)
Show that
1 - tan
2
A
cot
2
A - 1
= tan
2
A
L.H.S. =
1 - tan
2
A
cot
2
A - 1
=
1
1
-
2
A
2
A
2
A
2
A
-
1
1
[∵ tan A =
sin A
cos A
; cot A =
cos A
sin A
]
=
2
A -
2
A
2
A
2
A -
2
A
2
A
=
2
A -
2
A
2
A
×
2
A
2
A -
2
A
=
2
A
2
A
=
2
A = R.H.S.
Clear