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Cant get the Subs to input into my partial Derivatve

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This is my Code
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syms R1 R2 R3 R4 R5 R6 R7
f=R1+((R2+((R4*(R5+R6+R7))/(R4+R5+R6+R7)*R3))/((R3+R2+(R4*(R5+R6+R7))/(R4+R5+R6+R7))));
P=diff(f,R1);
subs(P,{R1,R2,R3,R4,R5,R6,R7},{220,150,270,100,330,47,390})
and to check it partial with respect to R1 shold be 220 I keep getting 1
Im trying to take the partial derivative of a long formula for Resistor Eq. and cant get the final value to display. Please help

Answers (1)

Walter Roberson
Walter Roberson on 18 Sep 2015
Your expression has R1 plus an expression that does not involve R1. Differentiate with respect to R1 and the answer is going to be diff(R1,R1) + diff(something independent of R1,R1) which is going to be 1 + 0 = 1.

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