Trigonometry is the science of relationships between the sides and angles of a right-angled triangle.
Ratios of sides of right triangle are called trigonometric ratios.
Consider triangle ABC right-angled at B. These ratios are always defined with respect to acute angle ‘A’ or angle ‘C.
|case I||case II|
|(i) sine A =||(i) sine C =|
|(ii) cosine A =||(ii) cosine C =|
|(iii) tangent A =||(iii) tangent C =|
|(iv) cosecant A =||(iv) cosecant C =|
|(v) secant A =||(v) secant C =|
|(v) cotangent A =||(v) cotangent C =|
Trigonometric Ratios of Some Specific Angles
Trigonometric Ratios of Complementary Angles