angle

问题 I've got a little Problem with the Math.cos() method. I know, I have to convert the angle to Radians before using Math.cos() . But if I just do: System.out.println(Math.cos(Math.toRadians(90)); It outputs: 6.123233995736766E-17 Math.sin() is working well. 回答1: From trigonometry: sin x ~= x, for small values of x sin x = cos x+pi/2 Because pi/2 can't be represented exactly in IEEE-754 Floating point, it means, that it must be off by some value x, i.e it is represented by pi/2 +- x, where x <

问题 I'm trying to create a 4D environment, similar to Miegakure's. I'm having trouble understanding how to represent rotations. The creator of Miegakure wrote this small article explaining he made a class for 4d rotors. http://marctenbosch.com/news/2011/05/4d-rotations-and-the-4d-equivalent-of-quaternions/ How can I implement the functions of this class ? In particular the functions to rotate vectors and other rotors, and getting the inverse ? I would appreciate some pseudocode examples. Thanks a

问题 I want to know how to work out the new co-ordinates for a point when rotated by an angle relative to another point. I have a block arrow and want to rotate it by an angle theta relative to a point in the middle of the base of the arrow. This is required to allow me to draw a polygon between 2 onscreen controls. I can\'t use and rotate an image. From what I have considered so far what complicates the matter further is that the origin of a screen is in the top left hand corner. 回答1: If you

问题 I\'m trying to determine the degree size of the field-of-view of a Droid Incredible smartphone\'s camera. I need to know this value for an application that I\'m developing. Does anyone know how I can find out/calculate it programmatically? 回答1: Unless there's some API call for that (I'm not an Android programmer, I wouldn't know), I would just snap a picture of a ruler from a known distance away, see how much of the ruler is shown in the picture, then use trigonometry to find the angle like

问题 I need to calculate the angle in degrees between two points for my own Point class, Point a shall be the center point. Method: public float getAngle(Point target) { return (float) Math.toDegrees(Math.atan2(target.x - x, target.y - y)); } Test 1: // returns 45 Point a = new Point(0, 0); System.out.println(a.getAngle(new Point(1, 1))); Test 2: // returns -90, expected: 270 Point a = new Point(0, 0); System.out.println(a.getAngle(new Point(-1, 0))); How can i convert the returned result into a

问题 I imagine that this is a simple question, but I\'m getting some strange results with my current code and I don\'t have the math background to fully understand why. My goal is simple, as stated in the title: I just want to find the point at some distance and angle from a center point. My current code: Point centerPoint = new Point ( 0, 0 ); Point result = new Point ( 0, 0 ); double angle = 0.5; //between 0 and 2 * PI, angle is in radians int distance = 1000; result.Y = centerPoint.Y + (int

问题 I want to find out the clockwise angle between 2 vectors(2D, 3D). The clasic way with the dot product gives me the inner angle(0-180 degrees) and I need to use some if statements to determine if the result is the angle I need or its complement. Do you know a direct way of computing clockwise angle? 回答1: 2D case Just like the dot product is proportional to the cosine of the angle, the determinant is proprortional to its sine. So you can compute the angle like this: dot = x1*x2 + y1*y2 # dot

问题 How would you find the signed angle theta from vector a to b? And yes, I know that theta = arccos((a.b)/(|a||b|)). However, this does not contain a sign (i.e. it doesn\'t distinguish between a clockwise or counterclockwise rotation). I need something that can tell me the minimum angle to rotate from a to b. A positive sign indicates a rotation from +x-axis towards +y-axis. Conversely, a negative sign indicates a rotation from +x-axis towards -y-axis. assert angle((1,0),(0,1)) == pi/2. assert

问题 I want to Rotate Image according to a specific angle in android ,some thing like a compass... I have this code...it works on drawPath() but i want to replace the path and the Drawing thing with image.. I tried to create a bitmap image ,DrawBitmapImage , but the image does not Rotate like the path..Any Help PLease? public void draw(Canvas canvas) { double angle = calculateAngle(currentLongitude, currentLatitude, targetLongitude, targetLatitude); //Correction; angle-=90; //Correction for

问题 Given 2 angles in the range -PI -> PI around a coordinate, what is the value of the smallest of the 2 angles between them? Taking into account that the difference between PI and -PI is not 2 PI but zero. Example: Imagine a circle, with 2 lines coming out from the center, there are 2 angles between those lines, the angle they make on the inside aka the smaller angle , and the angle they make on the outside, aka the bigger angle. Both angles when added up make a full circle. Given that each