Question

If A,B,C are the interior angles of triangle ABC prove that Tan(B+C) divided by 2 =cot A divided by 2​

Answer 1

Answer:

Sin[(B+C)/2]

Since A+B+C=180 for interior angles of triangle ABC.

then B+C=180-A.

NOW Sin [(180-A)/2]

=Sin[90-(A/2)] since Sin(90-A)=CosA

=Cos(A/2)