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Hello everyone!

I need some help writing a function from a text. Here's the text:

Quote:A fisherman stands on a cliff 25m above the water. He's reeling in the fish with the velocity 1.5m/s. How fast does the fish move when the line is 40m long?

Could I have some help with this? I know that I have to calculate the derivate f'(40) for the function that describes where how far from the cliff the fish is, and I know that the function f(x)=sqrt(x²-25²). Thing is that X changes over time; if the line is C meter from the beginning, the line's length at t seconds is C-1,5t, but how do I calculate f'(40)=sqrt((C-1,5t)²-25²)?

I hope you understand what I mean, it's a bit tricky to explain, especially since English is not my native language. If I'm unclear, please tell me and I'll try to rephrase this.

~Psyberion
Function for what? For graphing this relationship between the time and speed? I don't understand. The way I see it though it's a triangle, so it's basic Pythagorean Theorem ...