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MENTAL MATH: TiPs & TrIcKs for...

Trigonometry: Tangent

Use this to find out the sine of angles of 30°, 45° and 60° degrees. [Opposite leg/Adjacent leg]. Tan(45) = 1

(fig 9)

This circle helps to figure out if the tangent of any given angle in he I, II, III or IV cuadrants is positive or negative.

(fig 10)

The tangent of any angle in the I cuadrant, as in an angle from 0° to 90°, is positive (as well as the sine and cosine).

The tangent of any angle in the II cuadrant, as in an angle from 90° to 180°, is negative (as well as the cosine). Only the sine is positive.

The tangent of any angle in the III cuadrant, as in an angle from 180° to 270°, is positive. (Both the sine and cosine are negative.)

The tangent of any angle in the IV cuadrant, as in an angle from 270° to 360°, is negative (as well as the sine.) Only the cosine is positive.