Trig domain question

Question

Q: Which restricted one-to-one trig function has a domain of 0 ≤ x ≤ (pi)

(I couldn't find pi in the insert special character thing)

Answer 1

This function is f(x) = cosx with domain [0,π]

Answer 2

A restricted function passes the horizontal line test in the domain given. So, look at each of the graphs (sine, cosine, tangent) between 0≤x≤π to see which one passes the horizontal line test for a 1:1 function.

Sine does not pass in that domain

Cosine passes!

Tangent does not pass in that domain

Cosine it is!

I hope that helps!