Category: 1. Trig Identities

Special cases of the sum and difference formulas for sine and cosine yields what is known as the double‐angle identities and the half‐angle identities. First, using the sum identity for the sine, sin 2α = sin (α + α) sin 2α = sin α cos α + cos α sin α sin 2α = 2 sin α cos…

In these lessons we will learn the sum identities and difference identities for sine, cosine and tangent. how to use the sum identities and difference identities to simplify trigonometric expressions. how to use the sum identities and difference identities to prove other trigonometric identities. What are the Sum and Difference Identities? The following shows the…

The sine rule gives the relation between the angles and the corresponding sides of a triangle. For the non-right-angled triangles, we will have to use the sine rule and the cosine rule. For a triangle with sides ‘a’, ‘b’, and ‘c’ and the respective opposite angles are A, B, and C, sine rule can be given as,…

Trigonometric identities are equations that relate to different trigonometric functions and are true for any value of the variable that is there in the domain. Basically, an identity is an equation that holds true for all the values of the variable(s) present in it. For example, some of the algebraic identities are:(a + b)2 = a2 + 2ab + b2(a…

Trigonometric identities (trig identities) are equalities that involve trigonometric functions that are true for all values of the occurring variables. These identities are useful when we need to simplify expressions involving trigonometric functions. The following is a list of useful Trigonometric identities: Quotient Identities, Reciprocal Identities, Pythagorean Identities, Co-function Identities, Addition Formulas, Subtraction Formulas, Double…