TRIGONOMETRIC FUNCTIONS

FURTHER MATHEMATICS SSS2 FIRST TERM

WEEK 8

TRIGONOMETRIC FUNCTIONS

Contents

The basic trigonometric ratios can be defined in two ways:

(i)traditional definition;

(ii) modern definition.

Traditional Definition

The basic trigonometric ratios can be defined in terms of the sides of a right–angled triangle.

Ѳ₄ + Ѳ₁= 360◦

          Ѳ₄ = 360◦ - ѳ

SInѳ₁ = sin(360◦ + Ѳ) = -y = -sinѲ₁

: sin(360◦ + Ѳ) = -sinѲ

Cosѳ₁ = cos(360◦ + Ѳ) = -x = -cosѲ₁

: cos(360◦ + Ѳ) = -sinѲ

Tanѳ₄ =       tan (360◦ + Ѳ)=-y-x  = -tanѳ

          : tan(360◦ + ѳ) = -tanѳ

Hence in the third quadrant:

Sin(360◦ + ѳ) = -sinѳ

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