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**Find the derivative of (4995)/(1+.12cosθ), when θ = 120°**

**My attempt:**

d/dx [4995/(1+.12cosθ) = (4995)(-1)(1+.12cosθ)

Letting θ = 120°...

= (4995)(-1)(1+.12(-1/2))

d/dx [4995/(1+.12cosθ) = (4995)(-1)(1+.12cosθ)

^{-2}(.12)(-sinθ)Letting θ = 120°...

= (4995)(-1)(1+.12(-1/2))

^{-2}(.12)(-[itex]\sqrt{3}[/itex]/2)My calculator says that is about 587.478

But it's supposed to be about 10.253

I just started calculus, so I'm probably making some really basic mistake.