1. Trignometric Ratios

Trigonometric Ratios

🔹 What are Trigonometric Ratios?

Trigonometric ratios show the relationship between the sides and angles of a right-angled triangle.

These ratios help us calculate unknown sides or angles using a known angle.

🔹 Parts of a Right-Angled Triangle

When an angle θ is given:

  • Hypotenuse → longest side (opposite the right angle)

  • Opposite → side opposite to angle θ

  • Adjacent → side next to angle θ

🔹 The Three Main Ratios

Sine (sin θ)
Opposite / Hypotenuse

Cosine (cos θ)
Adjacent / Hypotenuse

Tangent (tan θ)
Opposite / Adjacent

🔹 Easy Way to Remember (SOH–CAH–TOA)

  • SOH → sin = Opposite / Hypotenuse

  • CAH → cos = Adjacent / Hypotenuse

  • TOA → tan = Opposite / Adjacent

✅ Lesson 1 Key Takeaway

✔ Trigonometric ratios connect angles and sides
✔ sin, cos, and tan are used only in right-angled triangles
✔ SOH–CAH–TOA makes formulas easy to remember