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Blue Geometry P20

I have found cos(B/2) = ((a+c)^2 - b(b-a))/(2a)(b+c), and I am not sure how to proceed from here.

Any help would be appreciated!

Note: this is for Winter Camp

Thanks for your patience here Charles!

Looks like you're on the right track. Few questions (as hints):

What does Law of Cosines tell us about cos(B)?
Can we turn this into an equation involving cos(B/2) using a trig. identity?

Combining this with your expression from above should give an equation you can solve for cos(B/2).

My work

Did you see the post in here about this?