How do you prove that #sinytany=cosy# is not an identity by showing a counterexample?
1 Answer
Jan 29, 2017
It is not an identity. See explanation.
Explanation:
We have
#sinytany=cosy#
This can be written as
#siny*siny/cosy=cosy" "# (#tany=siny/cosy# )
Solving this we get
#sin^2y=cos^2y#
This will be true only when
For example,
As a counterexample, we can say
but
Hope that helps!