Application of Basic Proportionality Theorem

Here we will prove that the internal bisector of an angle of a triangle divides the opposite side in the ratio of the sides containing the angle.

Given: XP is the internal bisector of ∠YXZ, intersecting YZ at P.

Application of Basic Proportionality Theorem

To prove: \(\frac{YP}{PZ}\) = \(\frac{XY}{XZ}\).

Construction: Draw ZQ  ∥ XP such that ZQ meets YX produced at Q.



1. ∠YXP = ∠XQZ

2. ∠PXZ = ∠XZQ

3. ∠XQZ = ∠XZQ

4. XQ = XZ

5. \(\frac{YX}{XQ}\) = \(\frac{YP}{PZ}\)

6. \(\frac{YX}{XZ}\) = \(\frac{YP}{PZ}\)


1. XP  ∥ QZ and YQ is a transversal

2. XP  ∥ QZ and XZ is a transversal

3. ∠YXP = ∠PXZ

4. ∠XQZ = ∠XZQ

5. XP ∥ QZ

6. By statement 4.


1. The above proposition is true for external division also.

So, \(\frac{YP}{ZP}\) = \(\frac{XY}{XZ}\)

Application of Basic Proportionality Theorem Image

2. Converse of the above proposition is also true.

So, if P is a point on YZ such that YP : PZ = XY : XZ then XP bisects the angle YXZ internally or externally.

9th Grade Math

From Application of Basic Proportionality Theorem to HOME PAGE

New! Comments

Have your say about what you just read! Leave me a comment in the box below. Ask a Question or Answer a Question.

Didn't find what you were looking for? Or want to know more information about Math Only Math. Use this Google Search to find what you need.

Share this page: What’s this?

Recent Articles

  1. Rupees and Paise | Paise Coins | Rupee Coins | Rupee Notes

    Dec 04, 23 02:14 PM

    Different types of Indian Coins
    Money consists of rupees and paise; we require money to purchase things. 100 paise make one rupee. List of paise and rupees in the shape of coins and notes:

    Read More

  2. Months of the Year | List of 12 Months of the Year |Jan, Feb, Mar, Apr

    Dec 04, 23 01:50 PM

    Months of the Year
    There are 12 months in a year. The months are January, February, march, April, May, June, July, August, September, October, November and December. The year begins with the January month. December is t…

    Read More

  3. The Story about Seasons | Spring | Summer | Autumn | Winter

    Dec 04, 23 01:49 PM

    The Four Seasons
    Kids let’s enjoy the story about seasons. Here we will discuss about the four seasons and the duration. Some months are too hot and some are too cold. The period of hot months is called the hot

    Read More