quote:Original post by alnite
Thank God, I am not you.
I guess you don''t plan on taking calculus.
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Ripped off from various people
Identity sin(A+B)=sin(A)cos(B)+sin(B)cos(A)
I guess you don''t plan on taking calculus.
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Ripped off from various people
I am in Pre-Cal right now so I guess that is why my dad made me memorize all those equations. Nice to know though. 
quote:
2sin(A)cos(A) = cos(A)
2sin(A) = 1
sin(A) = 0.5
and thus solve for A.
But you missed a solution, when cos(A) = 0... You should be wary of dividing with variable expressions when they can equal 0.
Here is a better way of solving the equation:2sin(a)cos(a) = cos(a)
2sin(a)cos(a) - cos(a) = 0
cos(a)(2sin(a) - 1)) = 0
So either cos(a) = 0 or (2sin(a) - 1) = 0.
Using a vector to rotate another vector without storing an angle, thus bypassing using sin and cos as much as possible? (sort of like a matrix, except just for rotation and scaling)
a.x = cos(angle)
a.y = sin(angle)
b = vector2(...);
c.x = a.x*b.x-a.y*b.y; // cos(a+b) = cos(a)cos(b)-sin(a)sin(b)
c.y = a.y*b.x+b.y*a.x; // sin(a+b) = sin(a)cos(b)+sin(b)cos(a)
(I think I messed up the cos(a+b) one, but the idea is the same)
a.x = cos(angle)
a.y = sin(angle)
b = vector2(...);
c.x = a.x*b.x-a.y*b.y; // cos(a+b) = cos(a)cos(b)-sin(a)sin(b)
c.y = a.y*b.x+b.y*a.x; // sin(a+b) = sin(a)cos(b)+sin(b)cos(a)
(I think I messed up the cos(a+b) one, but the idea is the same)
I used it several times for physics problems. If you have two sound waves of close frequencies and you add them, you get a new wave with some special properties (modulation,..). This happens with light too and diffraction/interference stuff.
quote:Original post by Muzzafarathquote:
2sin(A)cos(A) = cos(A)
2sin(A) = 1
sin(A) = 0.5
and thus solve for A.
But you missed a solution, when cos(A) = 0... You should be wary of dividing with variable expressions when they can equal 0.
2sin(a)cos(a) = cos(a)
2sin(a)cos(a) - cos(a) = 0
cos(a)(2sin(a) - 1)) = 0
So either cos(a) = 0 or (2sin(a) - 1) = 0.
Hey, I never said I was *good* at using it that way.
Richard "Superpig" Fine
- saving pigs from untimely fates, and when he''s not doing that, runs The Binary Refinery.
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ry. .ibu cy. .y''ybu. .abu ry. dy. "sy. .ubu py. .ebu ry. py. .ibu gy." fy. .ibu ny. .ebu
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