Graphs of Sine, Cosine and Tangent
Here are some nice graphs to look at ...
Plot of Sine
The Sine Function has this beautiful up-down curve (which repeats every 2π radians, or 360°).
It starts at 0, heads up to 1 by π/2 radians (90°) and then heads down to -1.
Plot of Cosine
Cosine is just like Sine, but it starts at 1 and heads down until π radians (180°) and then heads up again.
Plot of Sine and Cosine
In fact Sine and Cosine are like good friends: they follow each other, exactly "π/2" radians, or 90°, apart.
Plot of the Tangent Function
The Tangent function has a completely different shape ... it goes between negative and positive Infinity, crossing through 0 (every π radians, or 180°), as shown on this plot.
At π/2 radians, or 90° (and -π/2, 3π/2, etc) the function is officially undefined, because it could be positive Infinity or negative Infinity.
Inverse Sine, Cosine and Tangent
The Inverse Sine, Cosine and Tangent graphs are:
Here is Cosine and Inverse Cosine plotted on the same graph:
Cosine and Inverse Cosine
They are mirror images (about the diagonal)!
The same is true for Sine and Inverse Sine and for Tangent and Inverse Tangent. Can you see this in the graphs above?