Is the triangle with these sides a right triangle? 22mm, 26mm, 34 mm

If a^2 + b^2 = c^2, where c is always the longest side, then we have a right triangle. 
a = 22
b = 26
c = 34

Plug them into the pythagorean theorem formula
a^2 + b^2 = c^2
22^2 + 26^2 = 34^2
484 + 676 = 1156
1160 = 1156

The last equation is false, so the original equation is false for that given (a,b,c) triple

These sides do NOT form a right triangle.