🎬 Triangles and their properties · Class 7 maths · 3:25
Triangles and their properties: Class 7 maths video
Master triangle properties with Captain Calc. Learn angle sum property, exterior angle theorem, side length rules, and Pythagoras theorem with fun Class 7 practice.
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Transcript
0:00 Class 7 maths. Triangles and their properties.
0:04 Welcome to another superhero math mission with Captain Calc.
0:08 Today we will explore triangles and master all their secret properties together.
0:14 Types of Triangles, Medians, and Altitudes.
0:18 Triangles can be classified by side lengths as equilateral, isosceles, or scalene.
0:25 They are also classified by angles as acute, right, or obtuse.
0:30 Try this one. A triangle has side lengths 7 cm, 7 cm, and 10 cm. What type of triangle is it based on its sides?
0:42 Observe that two sides are equal to 7 cm.
0:46 A triangle with two equal sides is called isosceles.
0:50 So the answer is Isosceles.
0:53 Angle Sum Property of a Triangle.
0:56 The sum of all three interior angles of any triangle is always equal to 180°.
1:04 If you know two interior angles, subtract their sum from 180° to find the third angle.
1:12 Try this one. Two angles of a triangle are 45° and 75°. Find the third angle in degrees.
1:22 Add the two known angles: 45° + 75° = 120°.
1:31 Subtract from 180°: 180° - 120° = 60°.
1:40 So the answer is 60.
1:43 Exterior Angle of a Triangle.
1:46 An exterior angle of a triangle is formed when one of its sides is extended outwards.
1:52 The measure of any exterior angle equals the sum of its two interior opposite angles.
1:59 Try this one. Two interior opposite angles are 50° and 60°. Find the exterior angle in degrees.
2:09 Identify interior opposite angles: 50° and 60°.
2:15 Add them together: 50° + 60° = 110°.
2:22 So the answer is 110.
2:25 Side Inequality and Pythagoras Theorem.
2:28 In any triangle, the sum of the lengths of any two sides is strictly greater than the length of the third side.
2:36 In a right-angled triangle, hypotenuse² = base² + height².
2:42 Try this one. Can a triangle have side lengths 3 cm, 4 cm, and 8 cm? Write Yes or No.
2:52 Check sum of two shorter sides: 3 + 4 = 7.
2:56 Compare with third side: 7 is not greater than 8.
3:01 So, no triangle can be formed.
3:03 So the answer is No.
3:06 Your turn. What is the line segment connecting a vertex to the midpoint of the opposite side called? Pause the video, and try it.
3:17 The answer is Median.
3:20 Well done! Now try the practice and the quiz in this lesson on LearnFun.
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