If cos theta - sin theta = root 2 sin theta , then what is the value of cos theta + sin theta ?
  1. root 2 cos (theta /2) 
  2. (cosec theta) /2
  3. sin theta
  4. cos theta 
 
Answer :- cos theta = root2 sin theta + sin theta 
         => cos theta =  sin theta ( root 2 + 1 )
         => cos theta = sin theta ( root 2 +1) (root 2 -1 ) / (root 2 -1 ) 
         => cos theta = sin theta [ (root 2)^2 - 1] / root2 -1
         => costheta (root 2 -1) = sin theta (2-1)
         => root 2 costheta - cos theta = sintheta 
         => root 2 costheta = sin theta + cos theta  -----ans 
 
But there is no option .
 
 

Asked by sucharitasahoo1 | 26th Dec, 2017, 05:46: PM

Expert Answer:

Your steps are correct. Check options again.

Answered by Sneha shidid | 27th Dec, 2017, 11:22: AM