You have the angles labeled wrong. It should be the angle between the light ray and the normal (dotted line)
n1 sin(theta1) = n2 sin(theta2)
since n1 is less than n2 that means angle 1 (incident angle) has to be greater than the refracted angle which you didn't label. But if you use your labeling of the ray exiting, the refracted angle will be greater. That would violate snell's law.
And I don't think you can really say theta 1 = theta 2 without being given the value of the incident angle. I could be wrong just try plugging in an incident angle value and solve it to find the angle refracted as the ray leaves n2 and goes into n1.
But remember the angle is measured between the light ray and the normal (your dotted line perpendicular to the surface)
Labeling is wrong as the jtran7 said. But the angles are still the same. If you correctly label theta 1 and theta 2, theta1=theta2. So 90-theta1=90-theta2