i have this equation that i need to derive and find its maximum value for theta and then substitute that value into the equation and obtaining the solution
can you help me with that ?
the equation is 
y= (((cosd(theta).^2 +sind(x)*cosd(theta))^2)+(3*(sind(theta).^2+sind(theta)*cosd(theta))^2))^0.5');


would really appreciate the help.....

Eng. Saleh

you can find a local maximum with fminsearch or fminunc (optimization toolbox is required for the latter). 

you might have to use multiple starting points to find the global maximum though, but i have little experience with optimizing trigonometric functions, so maybe somebody else has more specific advice how to find the global maximum of such functions

"Saleh Habib Khajah" wrote in message <jsdfel$ire$1@newscl01ah.mathworks.com>...
> i have this equation that i need to derive and find its maximum value for theta and then substitute that value into the equation and obtaining the solution
> can you help me with that ?
> the equation is 
> y= (((cosd(theta).^2 +sind(x)*cosd(theta))^2)+(3*(sind(theta).^2+sind(theta)*cosd(theta))^2))^0.5');
>  
> would really appreciate the help.....

It's an expression, not an equation
Correct the "x", " ' " and " .^ "
Use cos, not cosd, etc
Replace sin with sqrt(1-cos^2)... (+/- ?)
Substitute z = cos
Constraint  -1<=z<=1
Minimize y^2

Hope thishelps.

Greg