Recent content by jmed

any help? still lost

A lighthouse is located off shore one mile from the nearest point P, on a straight coastline. The light makes 4 revolutions per minute. How fast is the beam of light moving along the shoreline when it is 2 miles from point P? lighthouse is one mile from point P...trying to find how fast beam of...

ok, so the circumference is 2 pi and that divided by 4 is pi/2. So I'm still confused on how to find how fast the beam is moving when 2 miles from point P.? The distance from the lighthouse to the point 2 miles from P is Sqrt of 5. ...

Any help?! I'm still unsure where to go with this?

what formula is going to be used to find the rate of the light beam?

awesome! thanks again!

so the hypotnuse is the unknown (d). the distance up the shoreline is 2. the distance from P to the light house is 1. How is the tan of theta d/1? wouldn't it be 2/d?

Homework Statement A lighthouse is located off shore one mile from the nearest point P, on a straight coastline. The light makes 4 revolutions per minute. How fast is the beam of light moving along the shoreline when it is 2 miles from point P? Homework Equations The Attempt at a...

so then x = 4 after 30 seconds and r is then = to 5. This equates to (480*4)/5 = dr/dt. Which equals 384 mph?

x = distance plane has traveled...dx/dt is equal to rate at which plane is traveling...r is distance from observer to plane 30 sec. later. dr/dt is equal to rate of distance from observer to airplane 30 sec later. dx/dt would equal 480mph. dr/dt is what I am trying to find.

I still need a rate tho. I have x*dx/dt= r*dr/dt. I am not sure how to use the 480mph and the 30sec to find a rate. Is dx/dt = 30sec?

a^2 + b^2 = c^2?? but then how do I differentiate?

It is 3 miles. I am confused on what to use? I thought 45-45-90 because I calculated x to be 4 which would make the hypotnuse 5...?

Ok so it is a 45-45-90? Then I can use law of sine? Also, the altitude is 3km. So if I use law of sine, I get d = 4.2426...i'm not sure how I can differentiate from here tho...

Would law of cosine come into play? d^2 = 1^2 + x^2 - 2*1*x cos90. Then from here differentiate?