Annoying Geometry Proof Questions Help Me (1 Viewer)

[Noobtron]

http://img363.imageshack.us/img363/7433/dsc00461fw1.jpg

These two links are questions have questions i need help with. From the first link i cant prove 15 or 16, for the rest i havent done them yet but feel free to post answers for them if you feel like some geometry but help with those 2 questions would be great.


http://img363.imageshack.us/img363/3300/dsc00463ih0.jpg

 

[Mattamz]

15. a)
let < BAM = < CAM = α (given since AM bisectes BC)
let < ABM = < ACM = β (= angles opp. = sides in iso. triangle)

therefore:
2α + 2β = 180 (angle sum triangle)
α + β = 90

therefore:
< BMA + α + β = 180 (angle sum triangle)
< BMA = 90

similarly
< CMA + α + β = 180 (angle sum triangle)
< CMA = 90

therefore AM is the perpendicular bisects of BC.