Published by:
CGP EDU Academic Team
Published on: August 12, 2026
In a triangle ABC, a: b: c = 4: 5: 6. Then 3A + B equals to :
Text Solution
Verified by ExpertsThe correct answer is:
D
a : b : c = 4 : 5 : 6 ∴ a = 4k, b = 5k , c = 6k
cos B = 
= 
cos A = 
= 
= 
cos 3A = 4 cos 3 A – 3 cos A
= 4 × 
– 3 × 
= 
– 
= 
= 
cos 3A = –cos B = cos ( π – B)
∴ 3A + B = π
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