Class 11 Maths Trigonometric Functions Trigonometric Ratios (Acute)

Trigonometric Ratios (Acute Angles)  Using this logic ,In right ΔABC

sine of ∠ A = P/H = BC/AC

cosine of ∠ A = B/H  = AB/AC

tangent of ∠ A = P/B = BC/AB

cosecant of ∠ A = 1/ sine of A = AC/BC

secant of ∠ A = 1/cosine of A  = AC/AB

cotangent of ∠ A = 1/tangent of A = AB/BC

The value of sin A or cos A never exceeds 1, whereas the value of sec A or cosec A is always greater than or equal to 1.

Trigonometric ratios of an acute angle in a right triangle express the relationship between the angle and the length of its sides.

The values of the trigonometric ratios of an angle do not vary with the lengths of the sides of the  triangle, if the angle remains the same.

Greek letter θ (theta) is also used to denote an angle

Let’s see the values of trigonometric ratios for angles 0°, 30°, 45°, 60° and 90°. From the table above you can observe that as ∠ A increases from 0° to 90°, sin A increases from 0 to 1 and cos A decreases from 1 to 0.

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