Question

If A,B and C are the interior
angles of a AABC, then what
is the value of Cos(A+B)/2​

Answer 1

Given, A, B, C are the interior angles of a triangle ABC
∴∠A+∠B+∠C=180
∴
2
∠A+∠B+∠C
​
=
2
180
​

∴
2
∠A+∠B+∠C
​
=90
∴
2
∠A+∠B
​
=90−
2
∠C
​

Now, taking cos on both sides. we get,
cos(
2
∠A+∠B
​
)=cos(90−
2
∠C
​
)
⇒cos(
2
∠A+∠B
​
)=sin(
2
∠

Answer 2

Answer:

Sorry only for point please sorry