Brain Exercise...
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Everybody brobably already knows the anser to this...
There is a boat tied up to a dock with a ladder on one side. At low tide the water is at the fifth rung (counting from the top and going down). If the tide rises four feet then what rung would the water be at?
NOTE: Each rung is half a foot apart.
There is a boat tied up to a dock with a ladder on one side. At low tide the water is at the fifth rung (counting from the top and going down). If the tide rises four feet then what rung would the water be at?
NOTE: Each rung is half a foot apart.
The following statement is not true.
The previous statement is not true.
The previous statement is not true.
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- Nakranoth
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- SekoETC
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So now I should dig up a riddle... great.
The formula for calculating the central angle in radians based on knowing values of x and y. The central point is (x0,y0).
Directions downwards and from left to right are positive. How does the radian value behave on different quadrants?
Code: Select all
+----------------------->
|0 . (x,y) +
| ___ /|
| **' '*/ |
| ** / **
| * / |*
|* / _| *
|* O_)__L| *
|* *
| * *
| ** **
| **- -**
| '''
V +
The formula for calculating the central angle in radians based on knowing values of x and y. The central point is (x0,y0).
Directions downwards and from left to right are positive. How does the radian value behave on different quadrants?
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- Nakranoth
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Code: Select all
+----------------------->
|0 | (x,y) NOTE: Values below are just for visualisation
| _I_ x0=1, y0=1
| **' | '**
| ** | ** 1: x=2, y= 0 2: x=0, y=0
| * 2 | 1 * Dx= 1, Dy= -1 Dx= -1, Dy = -1
|* | *
|#-------O-------#1
|* | *
| * 3 | 4 * 3: x=0, y= 2 4: x=2, y=2
| ** | **
| **- | -** Dx= -1, Dy= 1 Dx= 1, Dy= 1
| 'T'
V + |
0 1 2
Having origo in the upper corner and having the y direction reversed doesn't really have a big meaning.
Dx (delta x) = x - x0, Dy = y - x0
In 1, x > x0 and y <y0> Dx = positive, Dy = negative
In 2, x < x0 and y <y0> Dx = negative, Dy = negative
In 3, x <x0> y0. -> Dx = negative, Dy = positive
In 4, x > x0 and y > y0. -> Dx = positive, Dy = positive
tan a = Dy / Dx.
1: tan a = negative (-1)
2: tan a = positive (+1)
3: tan a = negative (-1)
4: tan a = positive (+1)
a = cot (Dy / Dx)
pi/4 = 0.7853981 rad = 45 deg
-pi/4-0.7853981 rad = -45 deg
The problem is as the angle goes over 90 degrees, it apparently doesn't care about that.
In low middle point, Dx = 0 and therefor creates an error due to division by zero.
In high middle point, Dx = 0 and Dy is also 0 so the result is 0/0 = 0.
In left middle point, Dy = 0 and Dx = -1
In right middle point, Dy = 0 and Dx = 1
Ah, screw this, I can't solve my own riddle.
Apparently pi/2, pi or 3/2 pi needs to be added depending on which quadrant is being handled. Fun.
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- Nakranoth
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Come on Seko, don't remember your Trig?
Every point in the circle forms a right triangle... the angle in radians of the central angle is derived using your arcsin, arccos, and arctan functions... such that, (useing a regular coordinate system) arctan of your y value, over your x value gives you the first or fourth quadrant equivelants... in order to tell weather or not this value is correct, however, check your x value, if it is negative, you need to add pi to your answer... also, where arctan doesn't exist, you simply check your y value for positive or negative sign, and you end up with pi/4 or 3pi/4 respectively... as for an equation for the "function" it can't exist because circles have multiple y values for given x values... soo... what was I talking about?
Every point in the circle forms a right triangle... the angle in radians of the central angle is derived using your arcsin, arccos, and arctan functions... such that, (useing a regular coordinate system) arctan of your y value, over your x value gives you the first or fourth quadrant equivelants... in order to tell weather or not this value is correct, however, check your x value, if it is negative, you need to add pi to your answer... also, where arctan doesn't exist, you simply check your y value for positive or negative sign, and you end up with pi/4 or 3pi/4 respectively... as for an equation for the "function" it can't exist because circles have multiple y values for given x values... soo... what was I talking about?
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- Pie
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- Nakranoth
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SekoETC wrote:How does the radian value behave on different quadrants?
I just realized that this was the question that was asked... I feel silly now... the radian value increases counterclockwise throught the first to fourth quadrents, then resets to zero at the end of the fourth quadrent... or keeps going, but becomes reducable to the... You know what... I don't even really care...

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