- #1

Helly123

- 581

- 20

## Homework Statement

Proof Cos (A-B) - tan(A-D) = (2cos A)/(sin 2A + sin 2B)

## Homework Equations

Cos(A-B) = cosA cosB + sinA sinB

Tan(A-D) = (Tan A - tan B)/(1+Tan A Tan B)

## The Attempt at a Solution

cosA cosB + sinA sinB - (tan A - tan B)/(1+Tan A Tan B)

Become

CosA cos B + sin A sin B - $$\frac {sin A cos D - sin D cos A} {cos A cos D + sin A sin D} $$

How to simplify it and proof it? It gets more complicated

Is there anyone interested too?