Bernard Lebel wrote: > Hello, > > I have this little math problem. I have this formula from wich I get a > dot product between two vectors. > > cos(ß) = A.B / |A|.|B| = -0.0634 > So this would give me radians, right?
No, it's the cosine of ß, which has no units (a cosine is a ratio of two lengths) > > Then if I use > > math.degrees( -0.0634 ) > > This gives me a value of -3.6325524211294193. > > However I have a book in front of me who says I should get a value of > 93.635 degrees. mmmmm > > Btw, in the book, the equation is written > > ß = cos-1(-0.0634) = 93.635, where -1 is actually an exponent. Maybe > I'm just interpreting this wrong? The -1 means inverse. You have cos(ß) = -0.0634 - you want to find the angle whose cosine is -0.0634, i.e. (inverse cosine)(-0.0634). Another name for cos-1 is arccosine. In Python it is math.acos(): >>> import math >>> math.acos(-0.0634) 1.6342388771557625 >>> math.degrees(_) 93.634990377223801 Kent > > > > Thanks > Bernard > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor > > _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
