Trigonometric Equations and Identities

To find the exact values of sine and cosine

To simplify the equation into a manageable form

To convert all angles to degrees

To memorize all trigonometric identities

Sine Rule

Tangent Identity

Pythagorean Identity

Cosine Rule

sinx is replaced with cosx

tan²x is replaced with sin²x + cos²x

sin²x is replaced with 1 - cos²x

cos²x is replaced with 1 - sin²x

To avoid using trigonometric identities

To prepare for factorization

To simplify the equation

To make the equation longer

Five

Two

Three

Four

Using radians instead of degrees

Forgetting to convert back to radians

Using the wrong trigonometric identity

Not simplifying the equation

Radians are more accurate

Radians are easier to calculate

Degrees are not used in trigonometry

The domain is often given in radians

Quadrant diagram

Unit circle

Calculator

Graph

Cosine is positive

Cosine is negative

Cosine is undefined

Cosine is zero

The triangle becomes an equilateral triangle

The triangle becomes an isosceles triangle

The triangle becomes a right triangle

There is no triangle