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# Trigonometry (Metric)

Learn, or revise, trigonometrical functions (and their reciprocals and inverses) and trigonometrical identities.

## Units

### Trigonometrical Functions

The functions \(\sin x\), \(\cos x\) and \(\tan x\), and their reciprocals and inverses.

The natural measure of angle, and its relationship with the traditional one.

Using trig functions to calculate the areas of shapes in the plane.

Trig functions evaluated at \(0\), \(\pi/6\), \(\pi/3\), \(\pi/3\) and \(\pi/2\), and their obtuse and reflex counterparts.

Values of \(x\) on which the trig functions are defined, and values of \(y\) they attain; periodicity I their graphs.

### Identities

Relations among trig functions.

The relation \(\cos^2\,x+\sin^2\,x\equiv 1\), and its counterparts.

Identities for sine, cosine and tangent of \((x+y)\).

Identities for sine, cosine and tangent of \((2\,x)\).

Inverting the trig functions; restricting the domain.