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I have 2 vectors linked by 1 point. Like this <----o---------> If I move 1 vector, how do I find the new position of the other vector if it has to face the opposite direction of the one I moved and has to keep his original lenght. The point they are both linked by cannot move. So the first vector is known, the starting point of the first vector is also known, the lenght of both vector is known, just need the end point of the 2nd vector.

Thank you.

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The vectors must rotate around the fixed point. Let thtat point be $(x_0,y_0)$. Then the endpoint of the first vector is $(x_0+r_1 \cos \theta, y_0+r_1 \sin \theta)$, where $r_1$ is the length of the first vector. The endpoint of the second is then $(x_0-r_2 \cos \theta, y_0-r_2 \sin \theta)$, where $r_2$ is the length of the second. Is this what you wanted?

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