Capítulo II · Neste capítulo você vai
Circular functions
- associate the axes of cosines, sines, tangents and cotangents to the cycle;
- find a real number by quadrant;
- recognize periodic functions and calculate their period;
- define in the cycle the sine, the cosine, the tangent, the cotangent, the secant and the cosecant;
- demonstrate signs, growth and periodicity of each of them;
- build graphs like $f(x) = a + b \operatorname{sen}(cx + d)$ and determine image and period.
In chapter I, each real number became a point in the cycle. Now each point in the cycle becomes a number: its ordinate is the sine, its abscissa is the cosine, and certain tangent and secant lines give the other four functions. As the point returns to the same place every $2\pi$, all these functions repeat themselves — they are periodic, and their graphs are the waves that describe tides, sounds, alternating currents and the movement of a pendulum.
