Engineering Circuit Analysis 10th Edition Chapter One Exercise Solutions
3 − 3sin
1. We need to solve 100 = 1 which is a transcendental equation. Let’s solve it
3sin
graphically. This can be done on a graphing calculator, plotting points by hand (with a
little iteration), or using MATLAB script similar to
q = linspace(0, 0.5 *pi/ 2,1000);
rel_err = 100 *abs(3 *q-3 *sin(q))./sin(q)/3;
plot(q,rel_err,'r.')
Expanding the plot and looking for a point close to 1%, we find a value of q = 0.245 radians
is about the limit for the linear approximation if 1% or better accuracy is required.
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Engineering Circuit Analysis 10th Edition Chapter One Exercise Solutions
2. We start by expressing the relative error for the first function in the form
(1 + x ) −
1
100 1+ x =1
1
1+ x
Which can be simplified to
(1 + x )(1 − x ) − 1 = 0.01
1
or x2 = 0.01 which has solutions x = 0.1.
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Engineering Circuit Analysis 10th Edition Chapter One Exercise Solutions
V
3. We begin by rearranging VC = V0 (1 − e −t / ) to yield t = − ln 1 − C where VC/V0 is
V0
specified but t is not. We proceed to construct the expression for relative error, using the
V V
approximation that ln 1 − C − C :
V0 V0
V VC
− − C + ln 1 −
V V0
Relative Error = 100 0
V
ln 1 − C
V0
Mercifully, the time constant (τ) cancels in the numerator and denominator. Thus,
−(−0.1) + ln(0.1)
(a) Relative Error = 100 = 5.1%
ln(0.1)
− (−0.5) + ln(1 − 0.5)
(b) Relative Error = 100 = 28%
ln(1 − 0.5)
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