Question

A right tringle , whose sides are 3 cm and 4 cm ( other than hypotenous ) is made to revlove about its hypotenous . Find the volume and surface area of the double cone so formed

Answer 1

Answer:

Step-by-step explanation:

Given that in a right angled triangle, whose sides are 3 cm and 4 cm(other than hypotenuse).

The double cone so formed by revolving this right-angled triangle ABC about its hypotenuse .

Hypotenuse AC = Ö( 32 + 42) = 5 cm

Area of ΔABC = (1/2) x AB xAC

⇒ (1/2) x AC x OB = (1/2)x 4 x3

⇒ (1/2) x 5 x OB = 6

⇒ OB = 12 / 5 = 2.4 cm.

Volume of double cone = Volume of cone 1 + Volume of cone 2

= (1/3) πr2h1 + (1/3)πr2h2

= (1/3) πr2(h1 + h2)

= (1/3) πr2(OA +OC)

= (1/3) x 3.14x(2.4)2 x(5)

= 30.14 cm 3