# maximum value of a function

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Akshay Pratap Singh on 13 Mar 2019
Edited: madhan ravi on 13 Mar 2019
Hi, I am trying to find the maximum value of 'Pa' in this code with respect to 'a' while others are known. I wrote a following program. where I am wrong. As I am new to matlab, please help me.
clear all
clc
syms a
K=((1+(kh/(1-kv)))/(cos(d)+sin(d)*tan(a-p)))*((1/tan(a))+nq*(lf-l));
Pa=0.5*g*(1-kv)*K*H^2;
solve(diff(Pa)==0,a)

Akshay Pratap Singh on 13 Mar 2019
0 to 1.5
Akshay Pratap Singh on 13 Mar 2019
But I want also an expression for a.
madhan ravi on 13 Mar 2019
The maximum value of Pa is inf when a is zero. Perhaps?

Yasasvi Harish Kumar on 13 Mar 2019
Hi,
clear
clc
syms a;
kh=0.1;
kv=0;
d=26*(pi/180);
p=39*(pi/180);
lf=0.2;
l=0.1;
nq=1.35;
g=18.4;
H=4;
kagq=((1+(kh/(1-kv)))/(cos(d)+sin(d)*tan(a-p)))*((1/tan(a))+nq*(lf-l));
Pa=0.5*g*(1-kv)*kagq*H*H;
possition = vpasolve(diff(Pa)==0,a); % a value for maxima
I think this should solve it.
Regards

#### 1 Comment

madhan ravi on 13 Mar 2019
The calculus approach is true but the result is not within the bounds 0 to 1.5 even if the range is specified in vpasolve() empty sol will be returned , meaning maxima does not exist in the given range.