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### Grade 4 - Mathematics4.2 Triangles

 A triangle is a 3 sided polygon. Triangles are two-dimensional figures. Triangles can be classified according to the relative lengths of their sides as: Equilateral triangle (3 sides of equal length) Isosceles triangle (two sides are of equal length) Scalene triangle (all sides have different lengths) Triangles can also be classified according to the their internal angles as: Right triangle (or right-angled triangle) has one 90° internal angle (a right angle). The side opposite to the right angle is the hypotenuse; it is the longest side in the right triangle. The other two sides are the legs of the triangle. An obtuse triangle has one internal angle larger than 90° (an obtuse angle). An acute triangle has internal angles that are all smaller than 90° (three acute angles). An equilateral triangle is an acute triangle, but not all acute triangles are equilateral triangles. An oblique triangle has only angles that are smaller or larger than 90°. It is therefore any triangle that is not a right triangle. The angles of a triangle add up to 180 degrees. The sum of the lengths of any two sides of a triangle always exceeds the length of the third side. That is called the triangle inequality. Example: A triangle with one obtuse angle and two sides equal. Answer: Acute Isosceles triangle Directions: Read the questions carefully and identify the type of triangle. Also draw an acute, obtuse, right, scalene, isosceles, equilateral triangle and show its properties.
 Q 1: A polygon with 3 sides is calledRectangleSquareTriangleQuadrilateral Q 2: A right angle isEqual to 90less than 90Greater than 90 Q 3: An obtuse angle isGreater than 90Less than 90Equal to 90 Q 4: An acute angle isGreater than 90Less than 90Equal to 90 Q 5: A figure that can be folded in half so that the 2 halves match issymmetricala polygonbenchmark Q 6: I have an obtuse angle and 2 equal sides. What am I?Obtuse Isosceles TriangleRight Scalene TriangleObtuse Equilateral TriangleAcute Isosceles Triangle Q 7: I have 3 acute angles and 3 equal sides. What am I?Obtuse Scalene TriangleAcute Scalene TriangleRight Equilateral TriangleAcute Equilateral Triangle Q 8: I have 3 acute angles and 2 sides the same length. What am I?Obtuse Scalene TriangleAcute Equilateral TriangleAcute Scalene TriangleIsosceles Acute Triangle Question 9: This question is available to subscribers only! Question 10: This question is available to subscribers only!