Question

Curved surface area of a conical cup is 308 cm square and base radius is 7 cm . Find the angle at the vertex of the cone

Answer 1

The vertex angle of the cone is 60°

Step-by-step explanation:

Curved surface area of conical cup = 308 cm²

Radius = 7 cm

Curved surface area $=\pi rl$

$308=\pi\times 7\times l$

$l=14$

Let the vertex angle be Ф

$\sin\dfrac{\theta}{2}=\dfrac{r}{l}$

$\sin\dfrac{\theta}{2}=\dfrac{7}{14}$

$\sin\dfrac{\theta}{2}=\dfrac{1}{2}$

$\sin\dfrac{\theta}{2}=\sin30^\circ$

$\dfrac{\theta}{2}=30^\circ$

$\theta=60^\circ$

#BAL

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