Let \(f\) be a function with its natural domain.
As we saw before, a domain number \(b\) is a zero of \(f\), if \(f(b) = 0\).
The point corresponding to the zero \(b\) is \((b, f(b)) = (b, 0)\), an intercept on the graph.
Here is the complete graph of the function \(G(x)\).
The graph has one intercept, which means that \(G\) has one zero, which appears to be \(2.4\).
The graph has another intercept: \((0, 1.7)\). This tells us that \(G(0)=1.7\). However, this is not really useful information in function analysis.
If this function was a model for some timed event, then perhaps \(t = 0\), would be important to interpret back to the situation, as initial information. That would be left for the interpretation of the model.
When analyzing a function, we are mostly interested in its zeros, which correspond to intercepts on the horizontal axis.
Here is the complete graph of the function \(G(x)\).
- Intercepts of graph: \((3,0)\) and \((7,0)\).
- Zeros of \(g\): \(3\) and \(7\).
Note: The intercepts are points on the graph. They are not zeros of the function. Function zeros are domain numbers. The intercepts on the graph visually encode a function zero as the first coordinate of the intercept.
Note: The \(y\)-intercept has nothing to do with function zeros.
Let \(P(w)\) be a function. The graph of \(y = P(w)\) is displayed below.
The graph appears to have two intercepts, not three. This means the function \(P\) has two zeros.
- Intercepts of graph: \((-5,0)\) and \((5,0)\).
- Zeros of \(P\): \(-5\) and \(5\).
Note: The intercepts are points on the graph. They are not zeros of the function. Function zeros are domain numbers. The intercepts on the graph visually encode a function zero as the first coordinate of the intercept.
Note: \(-8\) is in the domain. However, there is an open/hollow dot at \((-8,0)\). which means it is not there. The dot for \(-8\) is \((-8,4)\). \(-8\) is not a zero of \(P\).
Note: The \(y\)-intercept has nothing to do with function zeros.
Let \(K(z)\) be a function. The graph of \(y = K(z)\) is displayed below.
The graph appears to have no intercepts. That is because the whole graph is not drawn. The arrow tells us that the graph continues to go down to the right.
That means there is an intercept around \((-3.8,0)\).
\(-3.8\) is the only zero of \(K(z)\).
Let \(S(\theta )\) be a function. The graph of \(y = S(\theta )\) is displayed below.
The graph appears to have an infinite number of intercepts.
They occur at even integer.
The zeros of \(S(\theta )\) are
Here is a complete graph of \(K(v)\).
In this graph, \(y=2\) is a horizontal asymptote, which means the graph will slowly approach the asymptote and stay near it.
This tells that eventually the values of \(K\) approach \(2\) and stay near \(2\).
This tells that eventually the values of \(K\) will be away from \(0\).
The graph seems to suggest that after \(15\), the values of \(K\) are no longer near \(0\).
That would give \(K\) four zeros: \(3.9\), \(5.8\), \(10.2\), \(11.6\).
Here is a complete graph of \(p(t)\).
The graph has no horizontal intercepts. So, \(p\) has no zeros.
Core Functions
Some core functions have zeros and others do not.
Core constant functions do not have zeros, unless it is the Zero function. Then every domain number is a zero.
If the power is positive, then core power functions only have one zero and that is \(0\).
If the power is negative, then core power functions do not have zeros.
Sine and Cosine have an infinite number of zeros.
The zeros of \(\sin (\theta )\) are \(\{ k\pi \, | \, k \in \mathbb {Z} \}\)
The zeros of \(\cos (\theta )\) are \(\{ \frac {\pi }{2} + k\pi \, | \, k \in \mathbb {Z} \}\)
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more examples can be found by following this link
More Examples of Visual Features