math
posted by stephen .
A baseball player hits a line drive to center field. As he rounds second base, he heads directly for third, running at 20 ft/sec. How fast is the distance from the rnner to home plate changing when he is halfway to third base?

hang on 
Damon
aargh, did this yesterday, going to look
 math  bobpursley

oh well, did it again 
Damon
h^2 = 90^2 + x^2
h is hypotenuse
x is distance from third
where x = (4520t) so dx/dt = 20
2 h dh/dt = 2 x dx/dt
dh/dt = (x/h) (20)
at t = 0, x = 45 and h = 100.6
so
dh/dt = 8.94  Thanks Bob  I did it differently yesterday, same answer  Damon

math 
Damon
x^2 = (4520*t)^2 + 90^2
2 x dx/dt = 2 *(4520t) (20)
at x=sqrt(45^2+90^2) when t = 0
2 (100.6) dx/dt = 90*20
dx/dt = 8.94 ft/s
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