f(x) =

e^x, x<0

cos(pi x) , 0 < or equal x < or equal 1

x^2 - 3/2, x > 1

I need to prove that f is discontinuous at 1.(by manipulating inequalities, rather than using calculus)

I have,

we guess that f is discontinuous at 1, find one {Xn} in A such that

Xn ---> a but f(Xn) does not ---> f(a)

I am not sure what sequence to use, can anyone help?