1

IIT-JEE 1980

Subjective
Given $$y = {{5x} \over {3\sqrt {{{\left( {1 - x} \right)}^2}} }} + {\cos ^2}\left( {2x + 1} \right)$$; Find $${{dy} \over {dx}}$$.

Answer

$${{dy} \over {dx}} = \left\{ {\matrix{ {{5 \over 3}.{1 \over {{{\left( {1 - x} \right)}^2}}} - 2\,\sin \left( {4x + 2} \right),} & {x < 1} \cr { - {5 \over 3}.{1 \over {{{\left( {x - 1} \right)}^2}}} - 2\,\sin \left( {4x + 2} \right),} & {x > 1} \cr } } \right.$$
2

IIT-JEE 1979

Subjective
Find the derivative of $$$f\left( x \right) = \left\{ {\matrix{ {{{x - 1} \over {2{x^2} - 7x + 5}}} & {when\,\,x \ne 1} \cr { - {1 \over 3}} & {when\,\,x = 1} \cr } } \right.$$$
at $$x=1$$

Answer

$${ - {2 \over 9}}$$
3

IIT-JEE 1978

Subjective
Find the derivative of $$\sin \left( {{x^2} + 1} \right)$$ with respect to $$x$$ first principle.

Answer

$$2x\,\cos \left( {{x^2} + 1} \right)$$

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