How to get 2 angle values for an asin?

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Joshua D'Agostino
Joshua D'Agostino le 19 Jan 2015
Hey guys, I'm trying to solve for 2 angles that have the same sine value.
i.e. if x = asin(0.5), then x could be 30 degrees or 150 degrees.
I can't get this to come out though.
tried declaring a 1x2 symbolic variable x: [x1,x2], but if I try:
S = solve('x = asin(0.5)',x)
Then what I get out is:
x = 0.52... (30 degrees)
x1 = 0
x2 = 0
Can anyone help me out here? What am I doing wrong?
Thanks,
Joshua

Réponse acceptée

A Jenkins
A Jenkins le 19 Jan 2015
>> syms x
>> solve('0.5 = sin(x)',x)
ans =
0.52359877559829887307710723054658
2.6179938779914943653855361527329
  3 commentaires
A Jenkins
A Jenkins le 19 Jan 2015
arcsin is defined to only return the principal value. The documentation says:
For real elements of x in the interval [-1,1], asin(x) returns values in the interval [-pi/2,pi/2]. For real elements of x outside the interval [-1,1] and for complex values of x, asin(x) returns complex values.
Joshua D'Agostino
Joshua D'Agostino le 20 Jan 2015
Oh I see. Gotcha, cheers mate

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