A spherical iron ball of 10 cm radius is coated with a layer of ice of uniform thickness the melts at a rate of 50 cm³/min. When the thickness of ice is 5 cm, then the rate (in cm/min.) at which of the thickness of ice decreases, is :

The length of the perpendicular from the origin, on the normal to the curve,
x² + 2xy – 3y² = 0 at the point (2,2) is

If c is a point at which Rolle's theorem holds for the function,
f(x) = $${\log _e}\left( {{{{x^2} + \alpha } \over {7x}}} \right)$$ in the interval [3, 4], where a $$ \in $$ R, then ƒ''(c) is equal to

Let ƒ(x) = xcos^–1(–sin|x|), $$x \in \left[ { - {\pi \over 2},{\pi \over 2}} \right]$$, then which of the following is true?