any1 who got new senior mathematics three unit course please answer this question (1 Viewer)

[hsutler]

there is this question in chapter 25 (applications of calculus to the physical world) in the new senior mathematics three unit course which i have attempted and could not work out.

Plz whoever can answer question 2 in exercise 25 (a) answer it for me on the comp. Or at least provide me with the pointers for tackling the question.

thanks

 

[vds700]

let the distance of the manto the base of the lamp pole be x. Let the length of the shadow be s.

Answer the second part first.

You need to find ds/dt

ds/dt = ds/dx . dx/dt, you know that dx/dt = 1, so you need to find ds/dx. Use similar triangles to relate s and x.

 

[hsutler]

Thanks a bunch!!!
i used similar triangles but my teacher began to laugh at me so i thought it was wrong
but now i know it is right

thanks again