why can't I get a simpel solve function to work

this is my code:

syms x

eqn = sin(x) == 1;

solx = solve(eqn,x)

I have copied it of Matlabs own site.

This is what it is supposed to give: pi/2

this is what i get: x

what am i doing wrong?

[Torsten]

Which MATLAB version do you use ?

[Jacob Markussen]

I want to use it for:

syms t

o = @(z)  exp((-z.^2)/2);

p = 1/sqrt(2*pi)*integral(o,-1,1)  

p = 0.6827

h = 1/sqrt(2*pi)*integral(o,-t,t);

solve(h == 0.6827,t)

Answer 1

[Torsten]

    syms t z

    p = 0.6827;
    o = exp(-z^2/2);
    h = 1/sqrt(2*pi)*int(o,z,[-t t]); 
    sol = solve(h == p,t)