Question

4. Show that the function f:
R-Rgiven by f(x) = cosx
for all xER is neither one-one nor onto​

Answer 1

Since cos0 = 1 and cos2pie = 1
Hence function is not one one

For onto,
We know cosx belongs to [-1,1]
Therfore there is no image of 2.
Hence, cosx is not onto