wiz-icon
MyQuestionIcon
MyQuestionIcon
1
You visited us 1 times! Enjoying our articles? Unlock Full Access!
Question

How is cos(-x)=cosx?


Open in App
Solution

Prove the given identity:

The given expression is, LHS=cos-x

cos-x=sin90--x ...[cosx=sin90°-x]

=sin90°+x

=sin90°cosx+cos90°sinx ...[sina+b=sinacosb+cosasinb]

=cosx+0 ...[sin90°=1;cos90°=0°]

=cosx

=RHS

Hence, the given relation cos(-x)=cosx has been proved.


flag
Suggest Corrections
thumbs-up
3
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Trigonometric Ratios
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon