Question 818571

 there is only one right angle in a right triangle because, by definition, all three angles in a triangle MUST add up to {{{180}}} degrees

if you have two right angles, their sum is already {{{180}}} degrees; so, there will be no way to have third angle in the shape and you'd never get a triangle out of that

or

having two right angles would give you two parallel lines perpendicular to a third; so, you'd never get a triangle out of that either