maths
posted by sadia khan .
if two resistors of r1 and r2 ohms are connected in parallel in an electriccircuit to make a R ohm resistor, the value of R can be found from the equation 1/R= 1/r1+ 1/r2. if r1 is decreasing at the rate of 1 ohm/s and r2 is increasing at the rate of 0.5 ohm/s.at what rate is R changing when r1=75 phm and r2= 50 ohm.

if y=tan(2tan^1x/2), show that dy/dx=4(1+y^2)/4+x^2

if y=tan(ptan^1x), show tha (1+x^2)y1  p(1+y^2)=0