how can it find the cordinate of P2 if the distance betwin P1 and P2 is the same?
find the point new position
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$\begingroup$
geometry
vectors
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0Nice photo from Paris!, and welcome to MSE. You've our [tutorial](http://meta.math.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference) if in next future you need write also identities. Good luck. – 2017-02-10
1 Answers
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$P_2(x=x_1+rcosθ,y=y_1+rsinθ)$ , where $r=d(P_1,P_2)=\sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$
You can easily calculate $θ$ from the triangle $P_1P_3P_4$ and substitute it. This is if the line $P_1P_2$ is parallel to your horizontal axis, if not then you should find the angle between them also
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0thank u ,actualy my line is not nessery parallel to my axis ,can give me the also the equasion for calculating the angle in both cases – 2017-02-10
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0$sinθ=\frac{(P_3P_4)}{(P_1P_4)},cosθ=\frac{(P_3P_1)}{(P_1P_4)}$ Similarly for the axis – 2017-02-10
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0so the the finale Angle θ=θ1+θ2 where θ1 is the angle betwin P1P3P4 and θ2 is the angle for the axis – 2017-02-10
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0@Mr_M that seems correct – 2017-02-10