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avatar+270 

Find the equation of the line that is tangent to the curve

 

y = 3xcosx

 

at point (pi, -3pi)

 

The equation of this tangent line can be written in the form y=mx+b

 

 

-Would appreciate any help on solving this one!

 Feb 20, 2016

Best Answer 

 #4
avatar+270 
+10

I solved it. The solution is y=-3x 

 

(as b=0)

 

Thanks all for the help.

 Feb 20, 2016
 #1
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+1

answer is 2

 Feb 20, 2016
 #2
avatar+270 
0

Okay, but what would the equation of the line be in y=mx+b form?

gretzu  Feb 20, 2016
 #3
avatar
+1

it is y = 2bx+ 2- 6 x 5mx b2

 Feb 20, 2016
 #4
avatar+270 
+10
Best Answer

I solved it. The solution is y=-3x 

 

(as b=0)

 

Thanks all for the help.

gretzu Feb 20, 2016
 #5
avatar+131 
0

W*f is that. Ive done some complex math but that is something else

 Feb 20, 2016
 #6
avatar+270 
0

Differentiation (aka, derivatives).

gretzu  Feb 20, 2016
 #7
avatar+129852 
+10

y = 3xcosx

 

and the slope at any point on this cure is given by the derivative of this function.....so we have....

 

y ' = 3cosx - 3xsinx  =   3[cosx -xsinx]

 

So, the slope at (pi, -3pi)  =

 

y '(pi)  = 3 [ cos (pi)  - (pi) sin (pi)]   =  3 [-1  -  pi*0]  =   3 [-1]  = -3

 

And the equation  of the tangent line at this point =

 

y - (-3pi)  = -3(x - pi)

 

y + 3pi  = -3x + 3pi

 

y = -3x

 

 

 

cool cool cool

 Feb 20, 2016

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