0

Guest

Courses New

r and r2 r are unit vectors in the x-y plane making angles a and b with the positive x-axis. By considering r1 . r2 r r , derive cos (a − b) = cos a cos b + sin a sin b


r


and r2


r


are unit vectors in the x-y plane making angles a and b with the positive


x-axis. By considering r1 . r2


r r


, derive


cos (a − b) = cos a cos b + sin a sin b


Grade:

1 Answers

APURV GOEL
39 Points
12 years ago

if we write vectors in component form we get

R1 = R1cosa^i + R1sina^j

R2 = R2cosb^i + R2sinb^j

now taking dot product R1.R2 = (R1cosa^i + R1sina^j) . (R2cosb^i + R2sinb^j)

which is also equal to R1R2cos(a-b)

so we have R1R2cos(a-b) = (R1cosa^i + R1sina^j) . (R2cosb^i + R2sinb^j)

or cos (a − b) = cos a cos b + sin a sin b


Think You Can Provide A Better Answer ?

Other Related Questions on General Physics

View all Questions »

ASK QUESTION

Get your questions answered by the expert for free

Answer and earn gift vouchers

Win Gift vouchers upto Rs 500/-

View courses by askIITians

Design classes One-on-One in your own way with Top IITians/Medical Professionals

Click Here Know More

Complete Self Study Package designed by Industry Leading Experts

Click Here Know More

Live 1-1 coding classes to unleash the Creator in your Child

Click Here Know More

a Complete All-in-One Study package Fully Loaded inside a Tablet!

Click Here Know More