Page 1 :
Key Notes, Chapter-08, Introduction to Trigonometry, •, , Trigonometry is the branch of Mathematics which deals with the measurement of sides and, angles of the triangles., , •, , In a right triangle ABC, right-angled at B,, , •, , sin A =, , side opposite to angle A, side opposite to angle A, , cos A =, hypotenuse, hypotenuse, , s tan A =, , side opposite to angle A, side adjacent to angle A, , cos ec A =, tan A =, •, , 1, 1, ;sec A =, sin A, cos A, , sin A, 1, , tan A =, cot A, cos A, , If one of the trigonometric ratios of an acute angle is known, the remaining trigonometric, ratios of the angle can be easily determined., , •, , The values of trigonometric ratios for angles 0°, 30°, 45°, 60° and 90°., , •, , 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., , •, , sin (90° – A) = cos A, cos (90° – A) = sin A;, , •, , tan (90° – A) = cot A, cot (90° – A) = tan A;, , •, , sec (90° – A) = cosec A, cosec (90° – A) = sec A., , •, , sin 2 A + cos2 A = 1,, , •, , sec2 A – tan2 A = 1 for 0° ≤ A < 90°,, , •, , cos ec 2 A = 1 + cot2 A for 0° < A ≤ 90º.