Study Guides/Maths/Mid Point Theorem
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What is the Mid-Point Theorem?

In Geometry (Class 9 - Quadrilaterals and Triangles), the Mid-Point Theorem is one of the most important proofs. It reveals a fascinating relationship between the sides of a triangle.

Question (Click to Flip)

What is the mid point theorem?

Answer

The mid-point theorem states that the line segment connecting the mid-points of two sides of a triangle is parallel to the third side and is exactly half of its length.

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Key Facts

Theorem applies to: Triangles.

Condition: The points must be the exact mid-points of two sides.

Result 1: The joined line is parallel to the third side.

Result 2: The joined line is exactly half the length of the third side.

The Mid-Point Theorem Statement

The theorem states that: "The line segment joining the mid-points of any two sides of a triangle is parallel to the third side and is equal to half of it."

Understanding the Theorem with an Example

Imagine a triangle ABC.

  • Find the exact middle point of side AB and call it point 'D'.
  • Find the exact middle point of side AC and call it point 'E'.
  • Now, draw a straight line connecting D and E.

According to the Mid-Point Theorem, two magical things happen to this new line segment DE:

  1. It is Parallel: Line DE will be perfectly parallel to the bottom base line BC (DE || BC).
  2. It is Half the Length: If the bottom base BC is 10 cm long, the line DE will be exactly 5 cm long (DE = 1/2 BC).

The Converse of the Mid-Point Theorem

The reverse is also true. If you draw a line from the mid-point of one side (D), parallel to the base (BC), it will automatically hit the exact mid-point of the third side (E).

Questions and Answers

What is the mid point theorem?+

The mid-point theorem states that the line segment connecting the mid-points of two sides of a triangle is parallel to the third side and is exactly half of its length.

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