Question

In the diagram below, the y-coordinate of point P is increasing at a rate of 4 units per minute while point Q remains in its fixed position. Find the rate of change of angle, in radians per minute, when y = 20.

y
^
| P (0, y)
|
|
|
|
|---|
|___|________ Q (4, 0)

Then, P (0 , 20). Can you calculate the slope since we have two coordinates given?

(0, 20) (4, 0)

m = (y2-y1)/(x2-x1)
m = (0 - 20) / (4 - 0)
m = 5

Answer 1

The slope is actually -5. And forget I think i understand this now.

Answer 2

Let the angle formed by the line by Ø
then
tanØ= y/4
4tanØ = y
dy/dt = 4sec^2 Ø (dØ/dt)

when y = 20
tanØ= 20/4 = 5
secØ = √26/1 = √26
sec^2Ø = 26

then
4 = 4(26)dØ/dt
dØ/dt = 1/26 rads/min

Answer 3

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