📘 Class 10 Maths Chapter 19: Introduction to Trigonometry – Notes & Blog Post

 

🔍 What is Trigonometry?

Trigonometry is the branch of mathematics that deals with the relationship between angles and sides of a right-angled triangle.

It is widely used in geometry, physics, engineering, navigation, and even astronomy.

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📐 1. Trigonometric Ratios

In a right-angled triangle:

• Hypotenuse: the longest side (opposite to the right angle)

• Opposite side: side opposite to the angle

• Adjacent side: side next to the angle (but not the hypotenuse)

Let’s take angle θ:

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🔢 2. Trigonometric Ratios of Standard Angles

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📏 3. Trigonometric Identities

These are important equations that are always true for any value of θ (where defined):

1. $\sin^2θ + \cos^2θ = 1$

2. $1 + \tan^2θ = \sec^2θ$

3. $1 + \cot^2θ = \cosec^2θ$

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🧠 Tips for Remembering Ratios

Use this phrase to remember the basic three:

👉 "Some People Have // Curly Black Hair // Through Proper Brushing"

• Sin = Perpendicular/Hypotenuse

• Cos = Base/Hypotenuse

• Tan = Perpendicular/Base

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✅ Key Points to Remember

• Trigonometric ratios are only defined in a right-angled triangle.

• You must remember the values of standard angles.

• Practice converting one ratio into others using identities.

• Always check whether the value is defined or not for the given angle.

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📌 Real-life Applications

• Height and distance calculations

• Engineering designs

• Architecture and construction

• Physics: wave motion, optics

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📥 Download Chapter 19 Trigonometry PDF – (Coming Soon)
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