# Help would be gratly appreciated!

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#### pothitos

##### Guest
right i need some help with my maths homework, well not help really but information

does anyone know what happens to the coordinates of a point when they are reflected in the line y=-x. i have done the rest but i have run out of graph paper and i dont know the answer!

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#### Timeo27

##### Guest
Well, the x and y coordinates switch, like with reflections over y=x, but then they also become negative (or opposite). I think.

Give me a few minutes to test that theory. It's been awhile since I've worked with reflections and rotations.

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#### Timeo27

##### Guest
Yep. The reflection of the point (x,y) across the line y = -x is the point (-y,-x).

What level math are you in?

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#### pothitos

##### Guest
i think your right, the coordinates switch but the negative remains on the left hand side of the pair. for example if you had a set of axes -8 to 8 and you had a point at (-4,2) then if it was reflected on the line y=-x it would become (-2,4). well she can if it s not right

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#### pothitos

##### Guest
we normally have 2 papers, one with a calculator and one without. i seem to score higher on the non calc paper

#### dave holbon

##### Moderator
I’m useless at mathematics but it seems to me that any co-ordinates (two or more) that appear in a reflection or shadow have the original properties x,y inverted, (x,y)-z where z is the mirror image (minus or negative) plus another variable lets say (dv) to account for distortions introduced by the method of reflection in relation to the original. Plus another variable for all the distortions introduced from your viewing point back to the original (dz). This can include angular for say shadows (az), which are a sort of reflection, or logarithmic for size distortions (lz), or momentum for time distortions (tz) and I suspect that the mathematical formula which must be expressed as three objects where two must be known so as to calculate this from any perspective is horrendously complicated.

Attempting the same through a perfect mirror or substance with only one reflection does not produce any worthwhile answers.

Now you know why I’m useless at maths, I only understand the logic of a dartboard as viewed through a reflection in the bar overhead mirror.

Cheers

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#### pothitos

##### Guest
um yeah well i only need to know simple GCSE stuff but thatnks for posting. ill [size=huge]try[/size]and remember that

#### dave holbon

##### Moderator
It’s no good looking up the answer here, you must have an understanding of how to approach the problem and hence work out the answer yourself even if it’s wrong.

What will happen if you can’t locate the solution on the web? You will have to start thinking in the wild. This will give you the logical path to follow to answer any problem thrown at you in mathematical terms. Maths in simple it’s only adding and subtracting everything else is expressed as shorthand code (like logarithms) for a quick solution.

1 & 1 still equals 11. Nothing plus One plus one = 2

#### Electronic Punk

##### willalwaysbewithyou
Staff member
Political User
oh man ain't done that stuff for years...

But you can do it easily y=-x

1=-1 2=-2

so therefore it will start top right and move down to the bottom right.

#### Electronic Punk

##### willalwaysbewithyou
Staff member
Political User
oops not paying attention

I have forgotten the equation but you must add the inverse of the difference between the co-ordinates and where they cross teh line y=-x

#### Electronic Punk

##### willalwaysbewithyou
Staff member
Political User
There was an equation I used at A-level but I have forgottenit, check the paper that comes attached with any old exam paper, I am sure it will be there...

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#### denios

##### Guest
THAT'S IT!

homework.org...the new name of the site, God, I'm a genius...

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