Question

If A+B+C= π, then cos B+C/2 is.​

Answer 1

Answer:

-cos(A+C/2)

Step-by-step explanation:

FIRST

cos(A)=-cos(π-A)

SECOND

A+B+C= π means A+B+C/2+C/2= π

SO

π-(B+C/2)=A+C/2

SO

cos B+C/2 =-cos(A+C/2)