How to get all positive values of 'm' from the given domain of two variables?

Question

Atique Khan 2018-10-30

0
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https://ww2.mathworks.cn/matlabcentral/answers/427018-how-to-get-all-positive-values-of-m-from-the-given-domain-of-two-variables

关闭： MATLAB Answer Bot 2021-8-20

I have an equation in two variables naming a and b with domains 0.5 to 1 with step size equal to 0.01 for both a and b. I want to have all values of a and b on which the m results a positive number. The equation is given as and denominator is given separately. I make use of for loop to do so but it didnt work and I am new around with MATLAB to know the exactly how can I do this to be done.

 m(a,b)= (4*(a^2 + b^2)^(3/2)*(-8*a^3 + 8*a^3*b^3 +sqrt(a^2 + b^2)*(a^2 + 7*a^5 + b^2 + 7*a^3*b^2 -8*a^2*b^3 - 8*b^5)))/d

where

 d=15 *a^6 + 45* a^4* b^2 + 64* a^3* b^3 + 45* a^2* b^4 + 15* b^6 -64 *sqrt(a^2 + b^2) *(a^5 + a^3* b^2 + a^2* b^3 + b^5)

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Answer 1

Abhishek Kumar 2019-7-9

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i=1;
j=1;
cans=zeros(1,10);
lans=zeros(1,10);
for a=0.5:0.01:1
    for b=0.5:0.01:1
        d=15 *a^6 + 45* a^4* b^2 + 64* a^3* b^3 + 45* a^2* b^4 + 15* b^6 -64 *sqrt(a^2 + b^2) *(a^5 + a^3* b^2 + a^2* b^3 + b^5);
        m= (4*(a^2 + b^2)^(3/2)*(-8*a^3 + 8*a^3*b^3 +sqrt(a^2 + b^2)*(a^2 + 7*a^5 + b^2 + 7*a^3*b^2 -8*a^2*b^3 - 8*b^5)))/d;
        
        if m>0 
            cans(i)=a;
            lans(i)=b;
            i=i+1;
        end
    end
end