+0  
 
+1
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avatar+17 

Please explain the process.

 Dec 14, 2018
 #1
avatar+98172 
+2

By the Pythagorean Thorem :

 

z^2 = x^2 + y^2           differentiate both dides with respect to time, t

 

2z dz / dt   = 2x dx/dt   + 2y dy/dt

 

z dz/ dt   =  x dx / dt  +  y dy/dt

 

And dx/dt  =  3dy/dt  .....so...

 

z dz / dt  =  x (3 dy / dt) + y dy /dt

 

We have a      5 - 12 - 13     right triangle.....so when  x = 12 and y = 5, z = 13

 

So

 

13 dz / dt  =  12 (3 dy / dt) + 5 (dy / dt)

 

13 (1)   =  36 dy / dt  + 5 dy /dt

 

13 =  (36 + 5) dy /dt

 

13 = 41 dy /dt

 

(13/41) = dy /dt

 

And  dx /dt  =  3(dy /dt)  =  3 (13/ 41)  =  39/41

 

Thanks to Guest for pointing out my earlier silly error....!!!

 

 

cool cool cool

 Dec 14, 2018
edited by CPhill  Dec 14, 2018
 #2
avatar+17 
0

I think Cphill is right except the part where he says its a 12-5-17 triangle. If you use the pythagoreom theorem then z= 13

so dx/dt=39/41

 Dec 14, 2018
 #3
avatar+479 
0

Is CPhill a teacher?

awsometrunt14  Dec 14, 2018
 #4
avatar+98172 
0

Thanks, Guest.....stupid mistake....I'll make the edit  !!

 

 

cool cool cool

CPhill  Dec 14, 2018
 #5
avatar+479 
+1

Hey CPhill are you a teacher?

awsometrunt14  Dec 14, 2018
 #6
avatar+98172 
0

No.....I used to be a tutor at a Junior College....

 

 

cool cool cool

CPhill  Dec 14, 2018

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