Equation of Tangent

[roadrunner]

It turns out that the SLOPE function doesn't seem to work with expressions stored in variables so I had to make some changes to calculate the slope the old fashion way: by taking the first derivative.

Here's what i came up with:

PHP Code:

EXPORT TANGENT()
BEGIN
LOCAL f, B, fn, ff, sf;
PRINT;
INPUT (fn, "Function:", "f (X) =", "Enter the algebraic expression");
EXPR("F"+fn)▶f;
INPUT (A, "Study of the tangent at x =?", " X =");
PRINT ("f (X) =" + f);
PRINT ("Equation of the tangent at " + A + " :");
EVAL(subst(diff(f,'X',1),'X=A'))▶sf;
EVAL(subst(f,'X=A'))▶ff;
PRINT ("Y =" + sf + "(X -" + A + ") +" + ff);
−sf * A + ff ▶ B;
PRINT ("that is: Y =" + sf + IFTE(B<0,"X -","X +") + ABS(B));
END; 


On the first input statement enter an integer, n (0 to 9) and it will use function Fn from the symbolic view of the function app.

-road