Please wait...
1800-212-7858 (Toll Free)
9:00am - 8:00pm IST all days

or

Thanks, You will receive a call shortly.
Customer Support

You are very important to us

For any content/service related issues please contact on this toll free number

022-62211530

Mon to Sat - 11 AM to 8 PM

plz answer soon tomorrow is exam plzzzzzzzzzzz

Asked by BhavSimran 10th March 2010, 12:05 PM
Answered by Expert
Answer:

In ABC, let a, b and c be the lengths of sides opposite to the angles A, B and C respectively.

Draw a perpendicular from vertex A onto side BC. And call it AM.

Let BM = x, so that MC = a-x.

In ABM and ACM we can write using Pythagorus's theorem,

AM2 = c2-x2

AM2 = b2-(a-x)2

So that,

c2 - x2 = b2 - (a - x)2

c2 - x2 = b2 - a2 +2ax -x2

c2 = b2 - a2 +2ax

x = (c2 - b2 + a2)/2a

cosB = x/c

= (c2 - b2 + a2)/2ac

= (a2 + c2 - b2 )/2ac

Similarly we can write the expression for cosA and cosC.

It's called cosine rule.

Regards,

Team,

TopperLearning.

 

Answered by Expert 10th March 2010, 3:18 PM
Rate this answer
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10

You have rated this answer /10

Your answer has been posted successfully!

Latest Questions

NEET NEET Chemistry
qsnImg
Asked by lovespellbaba7 23rd June 2018, 1:26 AM

Chat with us on WhatsApp