TRIGONOMETRY – PART 1: BASICS OF
TRIGONOMETRY
Introduction to Trigonometry:
Trigonometry is a branch of mathematics that deals with the relationships between the sides and
angles of triangles. It is used in various fields like physics, architecture, engineering, and
astronomy. The word 'Trigonometry' comes from Greek words: 'trigonon' (triangle) and 'metron'
(measure).
Trigonometric Ratios of Acute Angles:
In a right-angled triangle ABC, where ∠B = 90°, we define trigonometric ratios for angle A as: sin A
= Perpendicular / Hypotenuse cos A = Base / Hypotenuse tan A = Perpendicular / Base cosec A = 1
/ sin A sec A = 1 / cos A cot A = 1 / tan A
Relations between Trigonometric Ratios:
sin A × cosec A = 1, cos A × sec A = 1, tan A × cot A = 1. Also, tan A = sin A / cos A and cot A = cos
A / sin A.
Trigonometric Ratios of Standard Angles:
Angle: 0°, 30°, 45°, 60°, 90° sin A: 0, 1/2, 1/√2, √3/2, 1 cos A: 1, √3/2, 1/√2, 1/2, 0 tan A: 0, 1/√3, 1,
√3, Not Defined
TRIGONOMETRY
Introduction to Trigonometry:
Trigonometry is a branch of mathematics that deals with the relationships between the sides and
angles of triangles. It is used in various fields like physics, architecture, engineering, and
astronomy. The word 'Trigonometry' comes from Greek words: 'trigonon' (triangle) and 'metron'
(measure).
Trigonometric Ratios of Acute Angles:
In a right-angled triangle ABC, where ∠B = 90°, we define trigonometric ratios for angle A as: sin A
= Perpendicular / Hypotenuse cos A = Base / Hypotenuse tan A = Perpendicular / Base cosec A = 1
/ sin A sec A = 1 / cos A cot A = 1 / tan A
Relations between Trigonometric Ratios:
sin A × cosec A = 1, cos A × sec A = 1, tan A × cot A = 1. Also, tan A = sin A / cos A and cot A = cos
A / sin A.
Trigonometric Ratios of Standard Angles:
Angle: 0°, 30°, 45°, 60°, 90° sin A: 0, 1/2, 1/√2, √3/2, 1 cos A: 1, √3/2, 1/√2, 1/2, 0 tan A: 0, 1/√3, 1,
√3, Not Defined
