Mary says the pen for her horse is an acute right triangle. is this possible? explain.

Generally speaking... yes! It is possible. It would just have to be less than 90 degrees to be considered acute.

That wouldn't be very comfortable for the horse.

Yes it is possible to have an acute right triangle. A right triangle means that there must be a single 90 degree angle somewhere on the triangle, leaving 90 degrees left for the other two angles. Since an acute angle is defined as being less than 90 degrees, the other two angles on the triangle must be acute angles. Therefore, you have a right triangle with 2 acute angles. So Mary is correct.

The answer is 60.9774