matlab, undefined function or method for input arguments of type double

I have read many of the posts related to this type of problem, however, unlike all the posts I have read my input argument is not a function it is a variable. What is also odd is that this variable is called successfully a few times prior to this error. I assume the error is due to a syntax error somewhere in my code but I can't for the life of me see it. I get the error on the first call for the variable ta:

Tp(i+1)=Tp(i)+ds.*(5.*(-wp(i)*gamma-(aa.*wp(i).*(TT(i)-ta(i))...
            /Rp(i))-2*(TT(i)-ta(i))*(hwa(i)-hwp(i))./(pi.*Rp(i)))...
            +8.*(-wp(i)*gamma-aa.*wp(i).*(Tp(i)-Ta(i))/Rp(i)-2*...
            (Tp(i)-ta(i))*(hwa(i)-hwp(i))/(pi.*Rp(i))));

but surprisingly I had no error just before this for this call:

TT(i)=Tp(i)+df.*(3.*(-wp(i)*gamma-(aa.*wp(i).*(Tp(i)-ta(i))/Rp(i))...
            -2*(Tp(i)-ta(i))*(hwa(i)-hwp(i))./(pi.*Rp(i))));

I am stumped. Can anyone explain why I am getting this error in this case?

Mahalo!

Andre

[Amit]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Moreover, post the full error as undefined function or method '.... '

Answer 1

[Walter Roberson]

Your third line is the only one that refers to Ta with a capital T. The other references are to ta with a lower-case t.