In this page, the importance of right angled triangles in application is explained. This justifies that problems of any polygon is simplified into right-triangles.

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Before going into details of right angled triangles, students need to understand one application scenario for the same.

A person walks `3` meter north and continues in the same direction for another `4` meter. What is the distance he has to walk to return back to the starting position?

- `3+4 = 7`
- `3+4 = 7`
- distance is not `3 + 4`

Since the person walks towards north all the time, the answer is '`3+4`'. *Two directional quantities add up in magnitude if they are in same direction.*

A person walks `3` meter north and continues towards east for another `4` meter. what is the distance he has to walk to return back to the starting position?

- `3+4 = 7`
- distance is not `3 + 4`
- distance is not `3 + 4`

Since the person walks in different directions, the answer is 'distance is not `3+4`'. *Two directional quantities do not add up in magnitude if they are not in same direction.* The result magnitude will be smaller to the magnitudes of the quantities being added.

A person walks `1` unit at angle `24^@` and then continues to walk `2.3` unit at angle `43^@`. The problem is illustrated in figure. How this can be solved to find the result?

- Principles of right angled triangles can help to solve
- Principles of right angled triangles can help to solve
- cannot solve using right angled triangles

The answer is "Principles of right angled triangles can help to solve"

The first walk of `1` unit at `24^@` is considered as hypotenuse of right angle triangle. The triangle is specified by three parameters 1. right angle 2. given angle 3. length of one side.

The same for the `2.3` unit at angle `43^@`, consider that as a right angled triangle. This two can be used to find the sides for the result `bar(OP)`.

How to find `bar(OP)`?

- Add components along x-axis
- Add components along y-axis
- Combine x & y axes components using Pythagoras theorem
- All the above in sequence
- All the above in sequence

Answer is 'All the above in sequence' as evident from the figure.

The distances covered at different angles is a good example of directional quantities. Principles and properties of Right angled triangles are useful to solve problems like that.

Where "sides of right angled triangles" are used in practice?

• Area of a quadrilateral is sum of area of two triangles. Any polygon can be handled as sum of triangles.

• Any triangle can be considered as combination of two right angled triangles.

• Directional quantities are best represented in orthogonal components. The orthogonal components are the legs of the right angled triangles.

• Some Directional quantities have their basis in rotational elements. An example is the induced electric current in a wire that rotates in a magnetic field. The angular speed of rotation is constant, and the directional quantity, derived out of it at a given angle `theta`, is a leg of the right angled triangle defined by `theta`.

• Length of a leg of a right angled triangle, as a function of angle, serves as a mathematical model for analysis.

Students may skip these if these are not easy to understand now. When you use the trigonometry in applications, you may return to refer and understand the above.

Right angled triangles play a significant role in orthogonal components of quantities with directions and orthogonal components of circular rotation.

**Application of Right-Angled-Triangle: ** Application can be classified into

• orthogonal components of quantities having direction.

• orthogonal components of quantities with circular rotation.

• mathematical model for analysis.

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