# Function and Relation Library — Squaring and Square Root Functions

How to write the inverse of the square root function
How to write the inverse of the square root function

The page Slope in Sound & Picture is useful in understanding slope.

The
slope
of the squaring function is 2x, twice the value of the x at a given point. Its
reciprocal
is 1/x2. For x values greater than or equal to zero, its
inverse is
x.

Squaring is useful in determining areas of plane figures. It is a widely used function.

When gravity and initial velocity and starting point are considered, but not wind resistance and angle of projection, thrown objects make parabolic, quadratic, paths.

These graphs are often used in examples in calculus.

The figure at the right shows a family of parabolas, y = ax2, where a takes values such as 4, 3, 2, 1, 1/2, 1/4, 1/10, -1/10, -1/4, -1/2, -1, -2, -3, and -4. Each parabola looks similar to the squaring function pictured above on this page. The larger the magnitude of the number, the skinner the parabola. The smaller the magnitude of the number, the fatter or flatter the parabola. If a is positive, the parabola is concave up (opens up). If a is negative the parabola is concave down (opens down). In each case the vertex, or point a which the U-shape bends, is (0,0).

Parabolas are quadratics. The quadratic equation and discriminants are useful in determining vertex and x-intercepts of the graph. The page The Quadratic Equation, Formula, & Discriminant should be very useful.

Parabolas are conic sections [discussed later]. Parabolas often describe situations in which area is computed or distance is computed. Displacement of objects shot into the air or dropped from a height are often described by quadratic functions.

 On Parabolas

The square root function is important because it is the inverse function for squaring. It tells what number must be squared in order to get the input x value.

The
square root
of a number, (n), may be explored using this link.

Its slope is 1/(2
x). When its domain is greater than or equal
to zero, its inverse is the squaring function. When its domain is all real
numbers, its range includes complex numbers such as i,
complex numbers.]

 On The Square Root Function

See The Laws of Exponents.

Though the symbol
for square root is familiar to many, a fractional
exponent is not.

Above, y =
x or y = xn when n = .5.

This means
x = x.5 or x1/2.
Other exponents are possible.

Pictures from pages on square root and index may help with vocabulary.

The cube root of x to the fifth,
3(x5), may be written as
x5/3.

In general, the bth root of x to the a power,
b(xa), is written (and
simplified as one might simplify fractions) as xb/a.

This page is from Exploring Functions Throught the Use of Manipulatives (ISBN: 0-9623593-3-5).

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