Let’s deduce formulas to calculate the trigonometric functions of $x$, with $x$ outside the 1st quadrant, relating $x$ with some number in the 1st quadrant. The goal is to know $\operatorname{sen} x$, $\cos x$ and $\operatorname{tg} x$ from a table that gives the circular functions of the reals between $0$ and $\frac{\pi}{2}$. Drag $P$ across all quadrants. The point $P'$ of the 1st quadrant is the symmetric point of $P$; Compare the sine and cosine values on the panel. Ative o JavaScript para ver esta figura interativa.
Fold a sheet in half, cut out a design on the fold and open it: the two halves are equal, one “reflecting” the other. This figure has symmetry. The axis of symmetry Definição · Axis of symmetry A figure has axis of symmetry when there is a line that divides it into two halves that meet fit perfectly when folding the figure along this line. Each half is the reflection of the other in a mirror.