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April 1, 2015

April 1, 2015

Posted by **Tim** on Sunday, March 9, 2014 at 10:40pm.

f(x) = 2 cos x + cos^2 x

at which the tangent line is horizontal. (Use n as your arbitrary integer.)

smaller y-value (x,y)=

larger y-value (x,y)=

- Calculus -
**Steve**, Monday, March 10, 2014 at 5:03amSince the derivative is the slope of the tangent line, we need

-2sinx - 2cosx*sinx = 0

-2sinx(1+cosx) = 0

sinx = 0 means x = nπ

cosx = -1 means x = (2n+1)π

so, f(x) has a horizontal tangent at x=nπ

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