No products in the cart.

Prove that the semi-vertical angle of …

CBSE, JEE, NEET, CUET

CBSE, JEE, NEET, CUET

Question Bank, Mock Tests, Exam Papers

NCERT Solutions, Sample Papers, Notes, Videos

Prove that the semi-vertical angle of the right circular cone of given volume and least curved surface area is cot–1 √2.
  • 1 answers

Gaurav Seth 3 years, 11 months ago

Solution:

Let V be the given volume of cone.

V=Volume of cone = 

h = Height of cone = 

C=Curved surface area of cone = , where r is radius and l is slant height of cone.

C= , as l²= r²+ h²

For Maxima and Minima, derivative of C that is curved surface area should be equal to zero.

K=C²= π²r²(r²+h²)

K =

Differentiating both sides with respect to r

K' = 4π²r³ + 

Putting , K'=0

=

h=

Let A be the semi vertical angle of the cone.

Cot A =  

       = 

Cot A= 

A= 

Hence proved.



 

http://mycbseguide.com/examin8/

Related Questions

Y=sin√ax^2+√bx+√c
  • 0 answers
Three friends Ravi Raju
  • 0 answers

myCBSEguide App

myCBSEguide

Trusted by 1 Crore+ Students

Test Generator

Test Generator

Create papers online. It's FREE.

CUET Mock Tests

CUET Mock Tests

75,000+ questions to practice only on myCBSEguide app

Download myCBSEguide App