Complex Related Rates: Points A and B move along the x- and y- axes, respectively,...

harveyandstanley

New member
Points A and B move along the x- and y- axes, respectively, in such a way that the perpendicular distance r from the origin to AB remains constant. How fast is OA changing and is it increasing or decreasing when OB=2r and B is moving toward o at the rate of 0.3r m/sec?

Subhotosh Khan

Super Moderator
Staff member
Points A and B move along the x- and y- axes, respectively, in such a way that the perpendicular distance r from the origin to AB remains constant. How fast is OA changing and is it increasing or decreasing when OB=2r and B is moving toward o at the rate of 0.3r m/sec?

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stapel

Super Moderator
Staff member
Points A and B move along the x- and y-axes, respectively, in such a way that the perpendicular distance r from the origin to AB remains constant. How fast is OA changing...
Which point is "O"? Does this mean "the origin"?

...and is it increasing or decreasing when OB=2r and B is moving toward o...
Does "o" mean "O", or is it a different point?

...at the rate of 0.3r m/sec?
Is the "r" supposed to be in the "rate" expression?

When you reply, please include a clear listing of your thoughts and efforts so far, starting with a scan of (or detailed description of) your initial drawing for this exercise. Thank you!

Subhotosh Khan

Super Moderator
Staff member
Points A and B move along the x- and y- axes, respectively, in such a way that the perpendicular distance r from the origin to AB remains constant. How fast is OA changing and is it increasing or decreasing when OB=2r and B is moving toward o at the rate of 0.3r m/sec?
Let the co-ordinate of the point A be[x[SUB]A[/SUB],0] and the co-ordinate of the point B be [0,y[SUB]B[/SUB]].

What is the equation of the line joining A and B?

What is the length of the perpendicular distance of a given point (here (0,0] to a given line (here AB)?