Question

In triangle ABC , angleA =60 .prove that BC2= AB2 + AC2-AB.AC
Please answer

Answer 1

I want to solve your question by the properties of Triangle,
cosA = (AB²+AC²-BC²)/2AB.AC
According to problem, angleA = 60⁰
So, 1/2 = (AB²+AC²-BC²)/2AB.AC
So, AB.AC = AB²+BC²-BC²
So, AB²+AC²-AB.AC = BC²


I hope you enjoyed.

Answer 2

Answer:

Step-by-step explanation:

cosA = (AB²+AC²-BC²)/2AB.AC

According to problem, angleA = 60⁰

So, 1/2 = (AB²+AC²-BC²)/2AB.AC

So, AB.AC = AB²+BC²-BC²

So, AB²+AC²-AB.AC = BC²