Find the derivative of the following functions (it is to be understood that a, b, c, d, p, q, r and s are fixed non-zero constants and m and n are integers):
cosec x cot x
Let f(x) = cosec x cot x
By product rule
f’(x) = cosec x (cot x)’ + cot x (cosec x)’ ……..(1)
Let f1(x) = cot x, accordingly f1(x + h) = cot (x + h)
By first principle
=
=
=
=
=
∴ (cot x)’ = - cosec2 x ………………..(2)
Let f2(x) = cosec x, accordingly f2(x + h) = cosec (x + h)
By first principle
=
=
=
=
=
= -cosec x cot x
∴ (cosec x)’ = -cosec x cot x ……………….(3)
Putting the value of (2) and (3) in (1)
f’(x) = cosec x (-cosec2 x) + cot x (-cosec x cot x)
= - cosec3 x – cot2 x cosec x