Unit 6 · Class 9 IB MYP · Formula Sheet
Trigonometry Introduction Formulas — Class 9 IB MYP
Define trigonometric ratios for right triangles and solve problems involving angles of elevation.
Key Formulas
SOH CAH TOA
\sin = \dfrac{O}{H}, \quad \cos = \dfrac{A}{H}, \quad \tan = \dfrac{O}{A}
Standard Angles
\sin 30° = \dfrac{1}{2}, \quad \cos 45° = \dfrac{\sqrt{2}}{2}, \quad \tan 60° = \sqrt{3}
Finding Angle
\theta = \sin^{-1}\left(\dfrac{O}{H}\right)
Pythagorean Identity
\sin^2\theta + \cos^2\theta = 1
Worked Examples
1Using: sin 30
Find sin 30 + cos 60.
Step 1: sin 30 = 1/2, cos 60 = 1/2.
Step 2: Sum = 1/2 + 1/2 = 1.
Answer: 1
2Using: tan identity
If tan A = 3/4, find sin A.
Step 1: In right triangle: opposite = 3, adjacent = 4.
Step 2: hypotenuse = 5. sin A = 3/5.
Answer: 3/5
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