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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: I have 3 acute angles and 2 sides the same length. What am I?Acute Scalene TriangleIsosceles Acute TriangleAcute Equilateral TriangleObtuse Scalene Triangle Q 2: I have an obtuse angle and 3 equal sides. What am I?Equilateral Obtuse TriangleObtuse Isosceles TriangleScalene Obtuse TriangleEquilateral Acute Triangle Q 3: A right angle isless than 90Greater than 90Equal to 90 Q 4: I have a right angle and all my sides are different. What am I?Right Scalene TriangleScalene Acute TriangleRight Isosceles TriangleAcute Equilateral Triangle Question 5: This question is available to subscribers only! Question 6: This question is available to subscribers only!