CameraIcon
CameraIcon
SearchIcon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

sin(n + 1)x sin ( n+2 )x + cos(n+1)x cos (n+2)x = cos x

Open in App
Solution

We have

cos(n+1)xcos(n+2)x + sin(n+1)xsin(n+2)x

it is from the identity

cos(a-b) = cosa * cosb + sina * sinb

here a= (n+1)x and b= (n+2)x

so,

= cos((n+1)x-(n+2)x)

= cos(nx+x-nx-2x)

= cos(-x)

= cosx { since cos(-x) = cosx }


flag
Suggest Corrections
thumbs-up
1
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Implicit Differentiation
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon