Question

Prove that: Δ=4.Rr cos a/2.cos b/2. cos y/2

Answer 1

help, pls

Answer 2

What is Rr and what is \(\Delta\) here represents??

Answer 3

radius and delta

Answer 4

Δ is the sign of delta !

Answer 5

Do you have a diagram for this question?

Answer 6

the question written above is the exact question from the book :)

The whole question is this :
Prove for any Δ ABC : Δ=4.Rr cos a/2.cos b/2. cos y/2, where all the symbols have thier usual meaning.

Answer 7

I understand that a, b are the angles, but not y, and delta.
Δ in ΔABC means triangle
Δ itself have the meaning of change, or discriminant. But I don't know the meaning of delta in this case, i.e. Δ = 4 r cos....

Answer 8

a, b , c are the sides -_-

Answer 9

No c in your question...

Answer 10

But I guess I'd better go, since I don't know how to solve your problem. I'm sorry!!

Answer 11

What is the radius of a triangle?

Answer 12

I mean radius is for circle right?

Answer 13

Can you type that out in latex/equation editor?

Answer 14

There is a lot of ambiguity with the symbols used here, but I'll try to interpret what I understand to be the question?

\( \displaystyle \triangle = 4 R r \cos \frac{\alpha}{2} \cos \frac{\beta}{2} \cos \frac{\gamma}{2}\)
Triangle, which I assume is area of the triangle ABC, is equal to 4 times R (the circumradius) times r (the inradius) times the cosine of each angle (where the y is an attempted translation of gamma.

I've never seen this identity so I don't know for sure if it is correct, but I'll try to research it more.