Trig Identity Question- Extension (1 Viewer)

[shazliz]

Help, I've just discovered Bored of Studies and hoping someone can help me with this question which is doing my head in.

If (a+b)/ cosec x = (a-b)/ cot x
show that
cosec . cot x= (a^2- b^2)/ 4ab

Didn't know how to type in- the question is from Cambridge 4F Q 18b. 18a was really easy but this one is making me run around in circles- any hints greatly appreciated!!

 

[anddwhat]

Derive that cos x = (a-b)/(a+b) then use the right angle triangle to derive cotxcosecx and then wallah!

 

[likeaBOS]

Derive that cos x = (a-b)/(a+b) then use the right angle triangle to derive cotxcosecx and then wallah!

How did you derive that equation for cosx?

 

[such_such]

What anddwhat is saying is:

 

[such_such]

oh yeah, and the cosecx & cotx is meant to be a sqrt(4ab) on the denominator