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Question

Question: \((fof)(2)\) is...

(fof)(2)(fof)(2) is

A

11/4

B

¾

C

½

D

None of these

Answer

¾

Explanation

Solution

limxπ41cot3x2cotxcot3x\lim _ { x \rightarrow \frac { \pi } { 4 } } \frac { 1 - \cot ^ { 3 } x } { 2 - \cot x - \cot ^ { 3 } x }

= limxπ4(1cotx)(1+cotx+cot2x)(1cotx)(cot2x+cotx+2)\lim _ { x \rightarrow \frac { \pi } { 4 } } \frac { ( 1 - \cot x ) \left( 1 + \cot x + \cot ^ { 2 } x \right) } { ( 1 - \cot x ) \left( \cot ^ { 2 } x + \cot x + 2 \right) }

= limxπ41+cotx+cot2xcot2x+cotx+2=34\lim _ { x \rightarrow \frac { \pi } { 4 } } \frac { 1 + \cot x + \cot ^ { 2 } x } { \cot ^ { 2 } x + \cot x + 2 } = \frac { 3 } { 4 }