Please tell me what's wrong here with the exp (1j*theta)
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I am trying to find the theta part from an exponential value.
Suppose, i take a variable
z=exp(1i*5);
so this will give me
z =
0.2837 - 0.9589i
Now i want to find that "5" from this value. So, i go with this "angle(z)" and matlab shows
ans =
-1.2832
Shouldn't it be 5, according to theory ??
Or if i go with the eular formula like, exp(i*theta)= cos(theta) + i*sin(theta)
so, theta= atan(0.2837/-0.9589) = -0.2877 !!
How do i get the theta=5 back, i don't know if i am missing something.
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John Doe
2013 年 5 月 11 日
編集済み: John Doe
2013 年 5 月 11 日
The reason is that:
5 rad = -1.2832 rad % (-1.2832 + 2*pi = 5)
That is:
x = x + n*2*pi; % where x is an angle in radians, and n is an integer.
Matlab will always give you values between +/- pi.
And you use Eular the wrong way around: tan = sin/cos, not cos/sin.
=)
- Rob
6 件のコメント
John Doe
2013 年 5 月 11 日
No. Valid angles are in the area (-pi < x < pi). Since 4 and 5 are outside this area, the angles are not 4 and 5 (but -1.283.. etc). However, 1 and 2 are within the valid area, thus the angle is equal to 1 and 2 (without adding any +/-k*2*pi).
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