Equation of Tangent

[vjc]

Hi all,
The HP prime does not show the equation of a tangent. It just draws a tangent.
I tried writing a program where I can put in an equation and specify the X value where the tangent is supposed to be, but am coming up with wrong answer. I am not very conversant with programming, Can anyone look into it and correct the program. Thanks.

TANGENT EXPORT ()
BEGIN
LOCAL f, B;
PRINT;
INPUT (f, "Function:", "f (X) =", "Enter the algebraic expression");
f ▶ F1;
INPUT (A, "Study of the tangent at x =?", " X =");
PRINT ("f (X) =" + F1);
PRINT ("Equation of the tangent at " + A + " :");
PRINT ("Y =" + SLOPE (F1, A) + "(X -" + A + ") +" + F1 (A));
−SLOPE (F1, A) * A + F1 (A) ▶ B;
PRINT ("that is: Y =" + SLOPE (F1, A) + "X +" + B);
END;