Question

in Triange ABC, prove cos (a+b) /2=sin(c/2)​

Answer 1

Step-by-step explanation:

cos(a+b) /2=sin(c/2)

On using the sine rule we know,

On using the sine rule we know,a/sin A = b/sin B = c/sin C = k

a/sinA=k

a=KsinA

b=ksinB

c=KsinC

now

a+b=k(sinA+sinB)

see pictures

last step

cos(A-B/2) /sin(c/2)

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