10) Three circles with centres A, B and C are mutually tangent and no circle lies inside another circle. The circle with centre A has a radius of 3 cm and the circle with centre B has a radius of 5 cm.
a) If angle BAC= 60 degrees, determine the radius of the third circle.
b) Find the area of triangle ABC
I drew a picture and went out on a wing and tried to use the cosine law:
Now that's all fine and dandy, but the answer at the back of the book says the answer is 2 cm! I don't know what to do!
12In any triangle ABC, prove:
I don't even know where to start...
Any help would be greatly appreciated!