6) In triangle ABC, AB=x cm, BC=5cm and AC=(10-x)cm:
Show that cos angle ABC=4x-15/2x
Where I have written cos angle it is shown in the book by a little triangle symbol with the right side missing, hope it actually means angle haha.
C2 help! Watch
- Thread Starter
- 01-02-2010 16:46
- 01-02-2010 17:49
you use a re-arrangement of the cosine rule.. so cos ABC = (AB)^2 + (BC)^2 - (AC)^2 all devided by 2*AB*BC .... and just sub in the number and you should get the answer (Btw ^2 means sqaured :P )