Introduction to Trigonometry Notes: Class 10 Maths Chapter 8

Short Note:

• For a right triangle with an acute angle θ: sinθ = opposite/hypotenuse, cosθ = adjacent/hypotenuse, tanθ = opposite/adjacent, and their reciprocals cosecθ, secθ, cotθ.

• tanθ = sinθ/cosθ and cotθ = cosθ/sinθ.

Short Note:

• sin: 0°=0, 30°=1/2, 45°=1/√2, 60°=√3/2, 90°=1.

• cos: 0°=1, 30°=√3/2, 45°=1/√2, 60°=1/2, 90°=0.

• tan: 0°=0, 30°=1/√3, 45°=1, 60°=√3, 90°=undefined.

Short Note:

• sin(90°−θ) = cosθ; cos(90°−θ) = sinθ; tan(90°−θ) = cotθ; cot(90°−θ) = tanθ; sec(90°−θ) = cosecθ; cosec(90°−θ) = secθ.

Short Note:

• sin²θ + cos²θ = 1

• 1 + tan²θ = sec²θ

• 1 + cot²θ = cosec²θ