MY CART (5)

Use Coupon: CART20 and get 20% off on all online Study Material

ITEM
DETAILS
MRP
DISCOUNT
FINAL PRICE
Total Price: Rs.

There are no items in this cart.
Continue Shopping
Menu
Grade: 8
        A+B+C =180° THEN VALUE OF COS2A + COS2B + COS2C = ? Pls.. give a proper explanation of the answer..
2 years ago

Answers : (1)

Arun
23013 Points
							
Dear Ritika
 
cos2A + cos2B + cos2C = 2cos(A+B).cos(A-B) + 2cos^2C -1 
=2cos(180-C).cos(A-B) + 2cos^2C -1 
= - 2cosC.cos(A-B) +2cos^2C -1 
= -2cosC(cos(A-B) - cosC) -1 
= -2cosC(cos(A-B) - cos(180-(A+B)) ) -1 
= -2cosC(cos(A-B) + cos(A+B)) -1 
= -2cosC( 2cosA.cosB) -1 
= -4cosAcosBcosC -1
 
Regards
Arun (askIITians forum expert)
2 years ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies


Course Features

  • 731 Video Lectures
  • Revision Notes
  • Previous Year Papers
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Test paper with Video Solution


Course Features

  • 31 Video Lectures
  • Revision Notes
  • Test paper with Video Solution
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Previous Year Exam Questions


Ask Experts

Have any Question? Ask Experts

Post Question

 
 
Answer ‘n’ Earn
Attractive Gift
Vouchers
To Win!!! Click Here for details