Gods Gift to Calculators: The Taylor Series It is incredible how far calculators have come since my parents were in college, which was when the square root key came out. Calculators since then have evolved into machines that can take natural logarithms, sines, cosines, arc sines, and so on. The funny thing is that calculators have not gotten any ” smarter’s ince then. In fact, calculators are still basically limited to the four basic operations: addition, subtraction, multiplication, and division! So what is it that allows calculators to evaluate logs, trigonometric functions, and exponents? This ability is due in large part to the Taylor series, which has allowed mathematicians (and calculators) to approximate functions, such as those given above, with polynomials. These polynomials, called Taylor Polynomials, are easy for a calculator manipulate because the calculator uses only the four basic arithmetic operators. So how do mathematicians take a function and turn it into a polynomial function? Lets find out.
First, lets assume that we have a function in the for my = f (x) that looks like the graph below. We ” ll start out trying to approximate function values near x = 0. To do this we start out using the lowest order polynomial, f 0 (x) = a 0, that passes through the y-intercept of the graph (0, f (0) ).
So f (0) = ao. Next, we see that the graph of f 1 (x) = a 0 + a 1 x will also pass through x = 0, and will have the same slope as f (x) if we let a 0 = f 1 (0).
The Business plan on Exponential and Logarithmic Functions Alvaro Hurtado
A function is a relation in which each element of the domain is paired with exactly one element in the range. Two types of functions are the exponential functions and the logarithmic functions. Exponential functions are the functions in the form of y = ax, where ”a” is a positive real number, greater than zero and not equal to one. Logarithmic functions are the inverse of exponential ...
Now, if we want to get a better polynomial approximation for this function, which we do of course, we must make a few generalizations.
First, we let the polynomial fn (x) = a 0 + a 1 x + a 2 x 2 +… + an xn approximate f (x) near x = 0, and let this functions first n derivatives match the the derivatives of f (x) at = 0. So if we want to make the derivatives of fn (x) equal to f (x) at x = 0, we have to chose the coefficients a 0 through an properly. How do we do this? We ” ll write down the polynomial and its derivatives as follows.
fn (x) = a 0 + a 1 x + a 2 x 2 + a 3 x 3 +… + 1 n (x) = a 1 + 2 a 2 x + 3 a 3 x 2 +… + nan xn-1 f 2 n (x) = 2 a 2 + 6 a 3 x +… +n (n-1) an xn-2… f (n) n (x) = (n! ) an Next we will substitute 0 in for x above so that 0 = f (0) a 2 = f 2 (0) /2! an = f (n) (0) /n! Now we have an equation whose first n derivatives match those of f (x) at = 0. fn (x) = f (0) + f 1 (0) x + f 2 (0) x 2/2! +…
+ f (n) (0) xn/ n! This equation is called the nth degree Taylor polynomial at x = 0. Furthermore, we can generalize this equation for x = a instead of just approximating about 0. fn (x) = f (a) + f 1 (a) (x-a) + f 2 (a) (x-a) 2/2! +… + f (n) (a) (x-a) n/ n! So now we know the foundation by which mathematicians are able to design calculators to evaluate functions like sine and cosine so that we do not have to rely on a table of values like they did in days past. In addition to the knowledge of how calculators approximate values of transcendental functions, we can also see the applications of Taylor series in physics studies.
These series appear in mathematical descriptions of vibrating strings, heat flow, transmission of electrical current, and motion of a simple pendulum.
