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📈 Optional Mathematics - Class 10
Lesson 7 · Height and Distance

Compound Angles Presentation

Optional MathematicsSubject
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Optional Mathematics, Class 10: Trigonometry

Compound Angles

A + B and A − B · Proof on the unit circle · Nine worked examples

By the end of this lesson you can

📐

Say what a compound angle is

⭕

Derive cos(A + B) on the unit circle

📝

Write all six compound angle identities

🔢

Find exact values such as sin 15° and tan 75°

✅

Prove identities by spotting the formula

How trigonometry grew

1
Egypt and Babylon: triangles for pyramids and stars
2
Hipparchus: tables from chords of a circle
3
Aarya Bhatta: sine (jya) and cosine
4
Islamic scholars: tangent and cotangent
5
Leonhard Euler: trigonometry as functions

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Presenter notes: Today we learn how to find the sine, cosine and tangent of two angles added together or taken apart. By the end you will find sin 15° exactly, without a calculator.