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## Comments

:

cos (x) = cos(-x)

To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

thanks all the same. but my query was how am i to find the oriented angle in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: :

:

: cos (x) = cos(-x)

:

: To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

:

thanks all the same. but my query was how am i to find the oriented angle in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: :

:

: cos (x) = cos(-x)

:

: To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

:

: thanks all the same. but my query was how am i to find the [b]oriented angle[/b] in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: : :

: :

: : cos (x) = cos(-x)

: :

: : To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

: :

:

What do you mean by "oriented angle"?

v1 v2 = |v1||v2| cos theta

where theta is the angle separating the 2 vectors

Ignoring the sign of the cos ratio, there would be 4 possible angles in a full cycle. 1 for each quadrant.

theta, 180 degrees - theta, 180 degrees+theta, 360 degrees - theta

Does that answer your question?

http://www.gamedev.net/reference/articles/article1832.asp

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what i want is this:

i have a tangent to a curve and want to find the angle that the tangent makes with the x-axis as the curve progresses. now this angle has to be the signed angle. how am i to obtain the 'signed angle' as the tangent makes different angles at different instances? hence, the problem is not for one parrticular dot product obtained angle. am i clear now? thanks a heap forsparing some time to help me out. thanks for the link to the site u quoted sephiroth!

have a great time!

amit

: : hi josh,

: : thanks all the same. but my query was how am i to find the [b]oriented angle[/b] in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : : : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: : : :

: : :

: : : cos (x) = cos(-x)

: : :

: : : To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

: : :

: :

:

: What do you mean by "oriented angle"?

:

:

: v1 v2 = |v1||v2| cos theta

:

: where theta is the angle separating the 2 vectors

:

: Ignoring the sign of the cos ratio, there would be 4 possible angles in a full cycle. 1 for each quadrant.

:

: theta, 180 degrees - theta, 180 degrees+theta, 360 degrees - theta

:

:

: Does that answer your question?

:

what i want is this:

i have a tangent to a curve and want to find the angle that the tangent makes with the x-axis as the curve progresses. now this angle has to be the signed angle. how am i to obtain the 'signed angle' as the tangent makes different angles at different instances? hence, the problem is not for one parrticular dot product obtained angle. am i clear now? thanks a heap forsparing some time to help me out. thanks for the link to the site u quoted sephiroth!

have a great time!

amit

: : hi josh,

: : thanks all the same. but my query was how am i to find the [b]oriented angle[/b] in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : : : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: : : :

: : :

: : : cos (x) = cos(-x)

: : :

: : : To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

: : :

: :

:

: What do you mean by "oriented angle"?

:

:

: v1 v2 = |v1||v2| cos theta

:

: where theta is the angle separating the 2 vectors

:

: Ignoring the sign of the cos ratio, there would be 4 possible angles in a full cycle. 1 for each quadrant.

:

: theta, 180 degrees - theta, 180 degrees+theta, 360 degrees - theta

:

:

: Does that answer your question?

:

: hi josh,

: what i want is this:

: i have a tangent to a curve and want to find the angle that the tangent makes with the x-axis as the curve progresses. now this angle has to be the signed angle. how am i to obtain the 'signed angle' as the tangent makes different angles at different instances? hence, the problem is not for one parrticular dot product obtained angle. am i clear now? thanks a heap forsparing some time to help me out. thanks for the link to the site u quoted sephiroth!

: have a great time!

: amit

: : : hi josh,

: : : thanks all the same. but my query was how am i to find the [b]oriented angle[/b] in one direction from, say the negative X-axis. the angle that i get is always the smaller of the two angles and how am i to get the other? this other may not always be the one i want. am i clear? :P

: : : : : whenever i want to find the angle between two vectors, i use the dot product method to find it and it gives me the smaller of the two possible angles. how am i to get the other?

: : : : :

: : : :

: : : : cos (x) = cos(-x)

: : : :

: : : : To get the other angle, you can just change the sign of the first angle or subtract it from 2*pi radiens (360 degrees).

: : : :

: : :

: :

: : What do you mean by "oriented angle"?

: :

: :

: : v1 v2 = |v1||v2| cos theta

: :

: : where theta is the angle separating the 2 vectors

: :

: : Ignoring the sign of the cos ratio, there would be 4 possible angles in a full cycle. 1 for each quadrant.

: :

: : theta, 180 degrees - theta, 180 degrees+theta, 360 degrees - theta

: :

: :

: : Does that answer your question?

: :

:

:

if you want to find the angle between a vector and the x-axis, you could always just use a unit vector in the direction of the x-axis,

i.e. theta = acos[(a b) / (|a||v|)] where a is your vector and b = <1, 0, 0>. that gives you the smaller angle. to get the larger one, just subtract theta from 2 * pi or 360 degrees.

hope that helps!

:

Hi Amit.

Not sure exactly what you mean, as there can only be one angle between two vectors. But I think I know what you mean. you could try negating one of the vectors and doing the dot product again. This will give you a 'big angle ' I hope its the one you want