Question

Q9) prove that:
((b ² - c ²)/a)•cos A
+ ((c ² - a ²)/b)•cos B
+ ((a ² - b ²)/c)•cos C
= 0
No irrelevant ans! Plz.​

Answer 1

Step-by-step explanation:

Given PQRS is a trapezium in which PQ || PS and PQ = 3 RS