A triangle can have two acute angles. Some examples of triangle types that have two acute angles are a right triangle and an isosceles right triangle.

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A triangle with two equal sides is called an isosceles triangle. The angles opposite the equal sides in an isosceles triangle are also equal. The third, unequal side of an isosceles triangle is called the base of the tri...

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A rectangle has four right angles and two pairs of equal sides. Rectangles are four-sided polygons known as quadrilaterals. Other types of quadrilaterals are the square, rhombus, trapezoid, parallelogram and kite.

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A scalene triangle has no parallel sides and no equal angles. The three noncongruent sides of a scalene triangle are of different lengths, and the measurements of the three unequal angles inside the triangle, like those ...

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The rules of a special right triangle concern the angles of the triangle. A special right triangle is one with the angles 30, 60 and 90 degrees. A right triangle with the angles 45, 45 and 90 degrees is another special t...

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The base angle theorem says if two sides of a triangle are congruent, then the angles opposite those sides must also be congruent. The converse is also true. If two angles of a triangle are congruent, then the opposite s...

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A triangle has either two or three acute angles, depending on the type of triangle. Right and obtuse triangles have two acute angles, whereas an acute triangle has three acute angles.

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