Which characteristics will prove that DEF is an acute isosceles triangle

- The angles in the triangle DEF must all be acute angles- angles smaller than a right angle (90 degrees) to prove an acute isosceles triangle. - The angles in the triangle DEF must all be acute angles- angles smaller than a right angle (90 degrees) to prove an acute isosceles triangle

the answer is 510

step-by-step explanation:

15 • 13 = 195

15 • 12 = 180

15 • 5 = 75

12 • 5 = 60

195 + 180 = 375

375 + 75 = 450

450 + 60 = 510

ok then what happened.