UPSC NDA Math Model Paper 3

Here, y = cos t
Differntiating w.r.t. t, we get

dy

dt

=−sin‌t ...... (1)
And x = sin t
Differntiating w.r.t. t, we get

dx

dt

=cos‌t ....... (2)
Now divide (1) by (2), we get

dy

dx

=−sin‌t∕cos‌t
=−x∕y
Hence, option (4) is correct.