MATLAB: How to find the range in the form of (a, b) of this function

functionmathrange

The range of f = (7*x +sin(x))/(x^2 + x + 2) is of the form [a,b]. Give a and b correct to two decimal places

edit – Not a homework question. Its a Test question for revision, has me stumped

so far, I have this

clear all 
syms x
hold on 
fplot(@fun2, [-6 6]);
hold off
x1 = fminbnd(@fun2, -6, 6);
y1 = fun2(x1)
y1 = sprintf('%0.2f',y1);
x2 = fminbnd(@fun2_neq, -6,6);
y2 = fun2_neq(x2)
y2 = sprintf('%0.2f',y2)

But wouldn't I need to specify fun2_neq and fun2 in different mfiles? Also, what would I specify it as?

Best Answer

You're missing a parenthesis. Is the 7*x over the quadratic, or just the sin is over the quadratic? Please fix the parentheses, then plot over -100 to 100 or something and see the shape of the curve. Make sure you use ./ instead of / and .^ instead of ^ and then you can do it without a loop, in just 3 lines of code (like I did). (Actually the range is the same no matter where you put the missing parenthesis.)

Related Solutions

MATLAB: INTEGRAL AT THE AREA

First define a function. This function must be able to accept an array and return an array. That is to say, if y1 = f(x1) and y2 = f(x2), where x1 and x2 are scalars, the function must also return [y1,y2] for f([x1,x2]). Actually the inputs will tend to be dozens or hundreds of elements long. There is more than one way to define a function in MATLAB, but the quickest is with the @ symbol. When you write @(x,y) it means that what follows that will be a function of x and y. That is to say, x and y will be treated as names of the variables of the function, and MATLAB will not try to evaluate the expression right then and there. So, it looks to me like you want to

1. First define x2, x3, y2, and y3. These will be scalar values. For example,

    x2 = 0;
    x3 = 1;
    y2 = 0;
    y3 = pi;

2. Define

    f = @(x,y) (x2*y3-x3*y2) + (y2-y3)*x + (x3-x2)*y

Normally, I would have told you to be sure to use .* instead of * because .* is element-by-element multiplication and * is matrix multiplication, but in this case you basically have an expression of the form a + b*x + c*y, where a, b, and c are scalars. When one argument is a scalar * and .* are the same operation. Note that if you want to change x2, x3, y2, or y3, you must define f again because when you create the function, it takes a snapshot of all the variables other than the arguments.

3. Perform the integral

    integral2(f,x2,x3,y2,y3)

MATLAB: How can one make this program work? (fmin question)

x=zeros(10,1);
for a=1:1:10
    x(a,1)=fminbnd(@(x) fun(x,a), 0, 2) % minimizes fun(x,a)
end

Best Answer

Related Solutions

MATLAB: INTEGRAL AT THE AREA

MATLAB: How can one make this program work? (fmin question)

Related Question