Curved surface area of a right circular cone is 154√2 sq cm and radius of the base 7 cm. Find its vertical angle.
WBBSE
Class X
Mathematics
Right Circular Cone
04 Mark
2025
Curved Surface Area (CSA) = π r l
or, 154√2 = π × 7 × l
or, 154√2 = \frac{22}{7} × 7 × l
or, 22 × l = 154√2
or, 22l = 154√2
or, l = 7√2 cm
Calculating Vertical angle (θ) :
sin θ\over2 = r / l
= 7\over7√2
= 1\over√2
sin θ\over2 = sin 45º
or, θ\over2 = 45º
or, Vertical angle (θ) = 2 × 45º = 90º
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