# TRIGONOMETRY

CONTENT

(a) Basic Trigonometric Ratios: (i) Sine (ii) Cosine (iii) Tangent with Respect to Right-angled Triangles.

(b) Trigonometric Ratio of: (i) Angle 30^{0} (ii) Angle 45^{0} (iii) Angle 60^{0}.

**Basic Trigonometric Ratios (i) Sine (ii) Cosine (iii) Tangent with respect to right-angled triangles.**

These trigonometric ratios are applicable to right – angled triangle. A right – angle triangle is 90^{0}. Thus the remaining two angles add up to 90^{0} since every triangle contains two right angles.

In ∆ABC, B + C = 90^{0}.

Such angles whose sum is 90^{0 }are said to be complementary angles. While capital letter are used for angles, small (lower case) letters are used for sides. Notice that the side opposite A is labelled a, the one opposite B is labelled b etc.

The side opposite the right angle is called the hypotenuse. Every right – angled triangle obeys the Pythagoras theorem. This theorem states that the square of the hypotenuse of any right angled triangle is equal to the sum of the square of the other two sides.

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