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simple math question

Started by CCF Jan 18, 2002 at 1:25 AM 7 replies 1.5k views

Original Post

Jan 18, 2002 at 1:25 AM

Hi there, It''s easier to understand this if it''s illustrated but lets say I have a point located in XY-coord at (100, 0). If I rotate the point 30 degrees (in any direction) at it''s base (0,0) where will the point be located now? I just need to know the method of calculating it. Thanks!

KalvinB

Jan 18, 2002 at 1:35 AM

Figure out the length of the line then find the sine or cosine of the angle the line will be at (are you moving it clockwise or counterclockwise?)

Then use the pathagorian theorum

Ben

[The Rabbit Hole | The Labyrinth | Programming | Gang Wars | The Wall]

Ironside

Jan 18, 2002 at 1:36 AM

newX = oldX * cos(30) - oldY * sin(30)
newY = oldY * cos(30) + oldX * sin(30)

replace 30 with any arbitray angle in degrees.

Edited by - ironside on January 18, 2002 2:37:14 AM

CCF

Author

CCF

Jan 18, 2002 at 1:41 AM

Thanks, guys! I''ll go try it out.

CCF

Author

CCF

Jan 18, 2002 at 2:09 AM

KalvinB:
Could you provide an algorithm to do it? I don''t fully understand the sine and cosine part (my math sucks...

). Direction of rotation doesn''t matter (anyway will do).

Ironside:
Hmmm... I couldn''t get it to work using the method you''ve provided (the point doesn''t rotate correctly from it''s base). Is there another way to do it or I might be implementing it wrongly?

Thanks!