Answer
(a) It is possible for a triangle to be an acute isosceles triangle.
(b) It is possible for a triangle to be an obtuse isosceles triangle.
(c) It is not possible for a triangle to be an equiangular isosceles triangle.
Work Step by Step
(a) It is possible for a triangle to be an acute isosceles triangle.
One angle has a measure of $x$ where $0 \lt x \lt 90^{\circ}$
The two other angles measure $\frac{180^{\circ}-x}{2}$
(b) It is possible for a triangle to be an obtuse isosceles triangle.
One angle has a measure of $x$ where $90^{\circ} \lt x \lt 180^{\circ}$
The two other angles measure $\frac{180^{\circ}-x}{2}$
(c) It is not possible for a triangle to be an equiangular isosceles triangle.
If all three angles measure $60^{\circ}$, then the triangle is an equilateral triangle, not an isosceles triangle.
