# Math Help - Basic Pullback Question

1. ## Basic Pullback Question

The book I'm using asks:

Let φ : R → R be given by φ(t) = et . Let x be the usual coordinate function on R. Show that φ*x = ex .

I can't figure this out and I don't understand why - what is the 'usual coordinate function' on R? I at first interpreted it as f(x) = x, but that doesn't make sense:

f : R → R given by f(x) = x. Then composing f with φ (the definition of pullback) gives φ*x = f(φ(t)) = et

Am I just doing something very stupid here?

2. ## Re: Basic Pullback Question

φ*x=φ*f(x)=f(φ(x))=φ(x)=e^x