Example 3. Plot the graph of the function $y=\sqrt{x}$.
Solution. The function $y=\sqrt{x}$ is defined when the expression under the root is non-negative, i.e., $x \geq 0$. Therefore, the domain of the function is the infinite half-interval $[0, \infty)$.

By squaring both sides of the given equation, we find $y^{2}=x$. The obtained equation defines a parabola for which the $O x$ axis will be the axis of symmetry.

Taking the square root, we get $y= \pm \sqrt{x}$. According to the condition, we need to take only the plus sign. Therefore, the desired graph is the part of the parabola for which $y \geq 0$ (Fig. 1.8).