If $y=2x\cos 2x-\sin 2x$, find $\frac{dy}{dx}$when $x=\tfrac{\pi }{4}$ 

If the gradient of the curve $y=2k{{x}^{2}}+x+1$ at x =  1 is 9. Find k 

Find the rate of change of the V of a sphere with respect to its radius r when r =1

Find the dimension of the rectangle of greatest areas which has a fixed perimeter p.

The slope of the tangent to the curve $y=3{{x}^{2}}-2x+5$at the point (1,6) is

If $y={{x}^{2}}-\frac{1}{x},$find $\frac{dy}{dx}$

Find the slope of the curve $y=2{{x}^{2}}+5x-3$at (1,4) 

Determine the maximum value of $y=3{{x}^{2}}-{{x}^{3}}$

Find the derivative of $(2+3x)(1-x)$with respect to x

Find the derivative o the function $y=2{{x}^{2}}(2x-1)$ at the point x = –1

The  radius of circular disc is increasing at the rate of 0.5cm/sec. At what rate is the area of the disc increasing when its radius is 6cm

The maximum value of the function $f(x)=2+x-{{x}^{2}}$is

Differentiate ${{\left( {{x}^{2}}-\tfrac{1}{x} \right)}^{2}}$ with respect to x

Differentiate ${{(\cos \theta -\sin \theta )}^{2}}$ with respect to θ

If $y={{(1+x)}^{2}},$find $\frac{dy}{dx}$

Find the derivative of $y=\frac{{{x}^{7}}-{{x}^{5}}}{{{x}^{4}}}$

Find the minimal value of the function $y=x(1+x)$

If $s=(2+3t)(5t-4),\text{ find }\frac{ds}{dt}$ when t = $\tfrac{4}{5}$secs.

The distance travelled by a particle from a fixed point is given as $s={{t}^{3}}-{{t}^{2}}-t+5$find the minimum distance that the particle can cover from the fixed point.