Question

What is surface area of cone ? ( tell me formula) and example.

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Answer 1

Answer:

Surface area of cone is

$\pi \: rl$

Answer 2

Answer:

$\large {\underline {\underline {\mathbf{Surface \: Area \: of \: cone:}}}}$

$\small \mathsf{Curved \: surface \: area  \: of \: a \: cone \: =\pi rl}$

$\small \sf{Total \: surface \: area  \: of \: a \: cone  \: = \pi r( l+r )}$

$\cal{l = \sqrt{ {h}^{2} + {r}^{2} } }$

Where, r is the base radius, h is the height and L is the slant height of the cone.

$\large {\underline {\underline {\mathrm {Example:}}}}$

Question 1: Find the total surface area of a cone, if radius is 8.2 cm and height is 16 cm.

Solution:

Given,

Radius r= 8.2 cm

Height h= 16 cm

Slant height,

$\small \cal{l = \sqrt{ {h}^{2} + {r}^{2} } }$

$\small \cal{l = \sqrt{ {16}^{2} + {8.2}^{2} } }$

$\small \cal{l = 17.98 \: cm}$

$\sf{Total \: surface \: area \: of \: a \: cone = }{\cal{\pi r(l + r)}}$

$\bf{Total \: surface \: area \:  of \: a \: cone \: }$

$\small \bf{ 3.14 \times 8.2(17.98 + 8.2) = 674.4cm²}$