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1
Lesson
Introduction to Trigonometry — Complete Lesson
?? Trigonometric Ratios
In a right triangle with angle ?:
sin ? = Opposite / Hypotenuse
cos ? = Adjacent / Hypotenuse
tan ? = Opposite / Adjacent = sin ? / cos ?
cos ? = Adjacent / Hypotenuse
tan ? = Opposite / Adjacent = sin ? / cos ?
"Some People Have Curly Brown Hair Through Proper Brushing"
Sin = Perpendicular/Hypotenuse • Cos = Base/Hypotenuse • Tan = Perpendicular/Base
?? Standard Values
| ? | 0° | 30° | 45° | 60° | 90° |
|---|---|---|---|---|---|
| sin ? | 0 | ½ | 1/v2 | v3/2 | 1 |
| cos ? | 1 | v3/2 | 1/v2 | ½ | 0 |
| tan ? | 0 | 1/v3 | 1 | v3 | 8 |
?? Key Identities
sin²? + cos²? = 1
1 + tan²? = sec²?
1 + cot²? = cosec²?
1 + tan²? = sec²?
1 + cot²? = cosec²?
2
MCQ Practice
Trigonometry — MCQ Practice
3
Memory Trick
Introduction to Trigonometry — Mnemonic
Mnemonic 1: SOH-CAH-TOA with a Bollywood Twist 🎬🎶
- Sin = Opposite / Hypotenuse
- Cos = Adjacent / Hypotenuse
- Tan = Opposite / Adjacent
Remember as: "Soh, Cah, Toa — Sunny Chacha Taught!" 😄
Imagine your favourite uncle (Chacha) Sunny explaining trigonometry with this catchy phrase!
Mnemonic 2: Hindi Phrase for SOH-CAH-TOA 🇮🇳📐
“साँप का टोआ” (Saanp Ka Toa) — Sounds like SOH-CAH-TOA!
- साँप (Saanp) = Sin = Opposite / Hypotenuse
- का (Ka) = Cos = Adjacent / Hypotenuse
- टोआ (Toa) = Tan = Opposite / Adjacent
Visualize a snake (साँप) pointing to sides of a triangle — easy to recall!
Mnemonic 3: Trigonometry Ratios as a Funny Story 🐀📏
“Some Old Horse Came A Hopping Through Our Alley”
- Some Old Horse = Sin = Opposite / Hypotenuse
- Came A Hopping = Cos = Adjacent / Hypotenuse
- Through Our Alley = Tan = Opposite / Adjacent
Imagine a silly horse hopping through your street to remember the ratios!
Interactive
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