RHS (Right angle-Hypotenuse-Side) - 7.2.5 | Chapter 2 : Triangles | CBSE Class 9 Maths
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7.2.5 - RHS (Right angle-Hypotenuse-Side)

Practice

Interactive Audio Lesson

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Introduction to RHS Criterion

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0:00
Teacher
Teacher

Welcome class! Today, we will dive into the RHS criterion for triangle congruence. Who can tell me what congruence means?

Student 1
Student 1

Does that mean the triangles are the same size and shape?

Teacher
Teacher

Exactly! Now, the RHS criterion is special because it applies only to right triangles. Can anyone tell me what a right triangle is?

Student 2
Student 2

A triangle with one angle of 90 degrees!

Teacher
Teacher

Correct! Now, if I say two right triangles have equal hypotenuses and one side, what can we conclude?

Student 3
Student 3

They are congruent based on the RHS criterion!

Teacher
Teacher

Right again! Remember, hypotenuse is the longest side of the triangle. Let's explore further!

Applying the RHS Criterion

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0:00
Teacher
Teacher

Let’s do a practical example! If we have two triangles, βˆ†ABC and βˆ†DEF where AB = DE and BC = EF, can you find how we would apply the RHS criterion?

Student 4
Student 4

We need to show that angle A and angle D are 90 degrees first.

Teacher
Teacher

Exactly! So if we confirm both angles are 90 degrees and the two sides are equal, we can say βˆ†ABC β‰… βˆ†DEF.

Student 1
Student 1

What if I could measure them and confirm they really are right triangles?

Teacher
Teacher

Good point! Measurements can confirm our criteria. That's the beauty of geometry!

Classroom Exercises on RHS

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0:00
Teacher
Teacher

Now let’s try some exercises to test your knowledge of the RHS criterion. Who can summarize what we need to check to prove congruence?

Student 2
Student 2

We need two triangles with equal hypotenuses and one corresponding side that are both right triangles.

Teacher
Teacher

Perfect! Let’s solve exercise 7.3 Q2. Triangle PQR and triangle XYZ are both right-angled and given such conditions. What do we do first?

Student 3
Student 3

Confirm that angle Q and angle Y are 90 degrees, then check the side lengths.

Teacher
Teacher

Exactly! And if both conditions hold true, can we conclude?

Student 4
Student 4

Then we conclude they are congruent!

Teacher
Teacher

Great teamwork! Recapping, the RHS criterion helps in identifying congruence in right triangles through two specific conditions.

Introduction & Overview

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Quick Overview

The RHS criterion is a method to prove the congruence of right triangles by comparing the hypotenuse and one side.

Standard

In this section, the RHS (Right angle-Hypotenuse-Side) rule is explored as a criterion for proving the congruence of triangles, particularly right triangles. The session emphasizes understanding how two right triangles can be deemed congruent if they have equal hypotenuses and one corresponding side.

Detailed

Detailed Summary

The RHS (Right angle-Hypotenuse-Side) criterion is crucial for establishing that two right triangles are congruent. This criterion states that if the hypotenuse and one other side of a right triangle are equal to the hypotenuse and one corresponding side of another right triangle, then the triangles are congruent. This section elaborates on the significance of congruence in geometry, particularly in solving triangle-related problems, ensuring that students not only understand the concept but can also apply it in different scenarios. Additionally, it reinforces properties of triangles and congruence criteria, emphasizing the unique role of the RHS criterion. Through exercises and discussions, students will learn to visualize these triangles and determine their congruence confidently.

Audio Book

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Understanding the RHS Congruence Criterion

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RHS (Right angle-Hypotenuse-Side): If the hypotenuse and one side of a right triangle are equal.

Detailed Explanation

The RHS criterion is a method to determine if two right triangles are congruent, meaning they are identical in shape and size. This rule specifically applies to right-angled triangles. To use this criterion, we look for the following: First, we must confirm that both triangles have a right angle (90 degrees). Next, we identify the hypotenuse, the longest side of the triangle opposite the right angle. We check if the hypotenuses of both triangles are equal. Finally, we need to verify that one additional side (not the hypotenuse) is congruent in both triangles. If these conditions are met, we can conclude that the two triangles are congruent based on the RHS criterion.

Examples & Analogies

Imagine you have two triangular pieces of cake cut from the same cake using a triangular knife. If both pieces have a right angle, and the longest side of both pieces (the hypotenuse) is exactly the same length, along with another side being equal, you can be sure these two triangular pieces are exactly the same shape and size, just like how RHS tells us about triangle congruence.

Application of RHS Congruence

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Prove the triangles are congruent (RHS Rule): In two right triangles, the hypotenuse and one side are equal.

Detailed Explanation

To apply the RHS rule in proving triangle congruence, follow these steps: First, identify both right triangles by confirming they each have a right angle. Second, measure the hypotenuse of both triangles and ensure they are equal. Then, check that one other side in each triangle is also of equal length. If these criteria are satisfied, we can use the RHS rule to state that the triangles are congruent, meaning they are identical in size and shape.

Examples & Analogies

Think of two right-angled ramps used for skateboarding. If both ramps are shaped as right triangles, and the height of the ramp (one side) is exactly the same in both cases and the length across the bottom (hypotenuse) is also identical, the ramps are indeed congruent. Skateboarders can confidently perform tricks on either ramp knowing they are the same.

Example Problem for Practice

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Triangle PQR is right-angled at Q, and triangle XYZ is right-angled at Y. Given: PQ = XY, PR = XZ. Prove βˆ†PQR β‰… βˆ†XYZ.

Detailed Explanation

In this example, to prove that triangles PQR and XYZ are congruent using the RHS criterion, start by confirming they are both right-angled at the specified vertices (Q and Y). Next, check the given lengths: PQ = XY (the hypotenuse) and PR = XZ (one additional side). Since both triangles share the right angle and have equal lengths for the hypotenuse and one other side, we can apply the RHS congruence criterion and conclude that βˆ†PQR is congruent to βˆ†XYZ.

Examples & Analogies

Imagine two wooden support beams used for a roof that are both right-angled. If one beam is labeled PQ and the other XY, and it is known that the distance from the base to the peak of both beams (the hypotenuse) is the same, plus the side supports are also the same length as PR and XZ, then you can be confident that both beams will provide the same stability and support since they are congruent triangles.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Right Triangle: A triangle with one angle measuring 90 degrees.

  • Hypotenuse: The longest side opposite the right angle in a right triangle.

  • RHS Criterion: A criteria for triangle congruence for right triangles based on equality of hypotenuse and one side.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • If triangle ABC has a right angle at C, and has hypotenuse AB, and BC = DE, then triangle DEF is congruent to triangle ABC if DE is equal to AB.

  • In triangle PQR, if PQ is the hypotenuse, and both PQ and PR are equal to XY and XZ respectively, we can declare them congruent.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • Triangles that are right, with sides that match, RHS shows them congruent, not a scratch!

πŸ“– Fascinating Stories

  • Imagine two adventurous triangles, Righty and Hypo. They travel the world, and wherever they find a match, they know they'll be congruent!

🧠 Other Memory Gems

  • Remember: R = Right, H = Hypotenuse, S = Side. R-H-S for understanding congruency!

🎯 Super Acronyms

RHS = Right Hippo Swings – Always remember that for right triangles; it’s the angles that sing!

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Congruent Triangles

    Definition:

    Triangles that are identical in shape and size.

  • Term: Hypotenuse

    Definition:

    The longest side of a right triangle, opposite the right angle.

  • Term: RHS Criterion

    Definition:

    A rule stating if the hypotenuse and one side of a right triangle are equal to another right triangle, the triangles are congruent.