Trigonometry Proving

-Wanderer- SG

Hi! Can someone help me solve this question:

Use the law of cosines and sin(A) = sin (B+C) to show the law of sines, i.e.

sin(A)/a = sin(B)/b = sin(C)/c

HyuugaNeji SG

http://jwilson.coe.uga.edu/EMT668/EMAT6680.2001/Mealor/EMAT%206700/law%20of%20sines/Law%20of%20Sines%20proof%201/lawofsinesproof1details.html

-Wanderer- SG

http://jwilson.coe.uga.edu/EMT668/EMAT6680.2001/Mealor/EMAT%206700/law%20of%20sines/Law%20of%20Sines%20proof%201/lawofsinesproof1details.html

Sorry but I don't see how this uses the cosine rule to prove the sine rule...

wee_ws SG

Hi,

I find it odd to prove the sine rule via the cosine rule.

The sine rule can be proven very simply by comparing the vertical components of two triangles, by dropping a perpendicular from a vertex to its opposite side.

The cosine rule can be proven by applying Pythagoras' Theorem.

Thanks!

Cheers,
Wen Shih