Manipal MET2016MathematicsApplication of Derivatives
If is the semi-vertical angle of a cone of maximum volume and given slant height, then is given by
Options
- A2
- B1
- C2
- D3
Correct answer
C. 2
Step-by-step solution
Volume of cone, V= 3 r^2 h V= 3 r^2 1^2-r^2 On differentiating w.r.t. I , we get d V d r = 3 [2 r 1^2-r^2 + r^2 2 1^2-r^2 (-2 r) ] Put d V d r =0 , we get r= 1 2 3 At r=1 2 3 , d^2 V d r^2 0, (maximum) h= I^2- 2 3 l^2 = 1 3 In A B C, = r h = 1 2 3 1 / 3 = 2