1. Since it is an isosceles triangle, we know that the two length sides have to be the same. Therefore, the angles across from the sides are the same. They cannot be 90 degrees or above because 90+90+0 would mean we would have all the interior angles at 180 but the thing is the third angle cannot be zero. Therefore, the other two angles cannot be 90 or more. They must be acute.
Also, if it had two right angles (90 degrees) or more, it could not close to be a triangle.
