If you begin with a right triangle with sides a, b, and c and decrease the right angle so it is an acute angle, how does a^2 + b^2 compare with c^2 ?

Answer 1

You can see that by drawing the right triangle and them making tyhe right angle smaller, with the same side lengths. c^2 becomes less.

Or you could take a look at the law of cosines.

c^2 = a^2 + b^2 - 2 a b cos C

cos C = 0 for a right triangle, but becomes more positive when the angle C is made acute