1. Basic trignometric identities

Basic Trigonometric Identities

🔹 What are Trigonometric Identities?

Trigonometric identities are formulas that are always true for any valid angle.

They help in:

  • Simplifying expressions

  • Solving problems easily

  • Connecting different ratios

🔹 Basic Trigonometric Identities

1️⃣ Pythagorean Identity
sin²θ + cos²θ = 1

This identity comes from the right-angled triangle and is very important.

2️⃣ Tangent Identity
tan θ = sin θ / cos θ

This shows how tangent is related to sine and cosine.

3️⃣ Reciprocal Identity (Sine)
sin θ = 1 / cosec θ

4️⃣ Reciprocal Identity (Cosine)
cos θ = 1 / sec θ

5️⃣ Reciprocal Identity (Tangent)
tan θ = 1 / cot θ

🔹 Easy Tip to Remember

  • sin ↔ cosec

  • cos ↔ sec

  • tan ↔ cot

They are reciprocals of each other.

✅ Lesson 2 Key Takeaway

✔ Identities are always true
✔ They connect different trigonometric ratios
✔ Useful for solving and simplifying problems