The perimeter of a triangle ABC is 6 times the arithmetic mean of the sines of its angles. If the side a is 1, then ∠A is :
Answer & explanation
Correct answer: option 1
$∑a=6\frac{∑\sin A}{3}⇒∑a=2∑\sin A$
$⇒K∑\sin A=2∑\sin A⇒K=2$
Now $\frac{a}{\sin A}=2⇒A=30°$