# Impedance and Trig Functions

Discussion in 'Homework Help' started by AnthonyWDJr, May 10, 2012.

1. ### AnthonyWDJr Thread Starter New Member

Mar 8, 2012
3
0
Gents,

The value of impedance has two components; resistive and reactive. Which trig function do we use to find the reactance when impedance is given and which trig function do we use to find the resistance when impedance is given?

Thanks,

Tony D.

2. ### Papabravo Expert

Feb 24, 2006
10,173
1,797
You don't need to use trigonometric functions. If you have a complex number like a + jb then the real part, a, is the resistance, and the imaginary part b is the reactance.

Now if the complex number is specified in polar form as a magnitude, Z, and an angle θ, then you can compute the real and imaginary parts as follows:
Code ( (Unknown Language)):
1.
2. Resistance = a = Re(Z,θ) = Z*cos(θ)
3. Reactance  = b = Im(Z,θ) = Z*sin(θ)
4.
The inverse transformations are
Code ( (Unknown Language)):
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2. Z = SQRT(a^2 + b^2)
3. θ = arctan(b/a) = tan^-1(b/a)
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