# Differential of cos(piy)Watch

Thread starter 2 years ago
#1
How do I differentiate cos(piy)?

Should I use chain rule??
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2 years ago
#2
The differential of any cos(f(x)) is -f'(x)sin(f(x))

Eg d(cos(2x))/dx = -2sin(2x)
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Thread starter 2 years ago
#3
(Original post by Cerdic)
The differential of any cos(f(x)) is -f'(x)sin(f(x))

Eg d(cos(2x))/dx = -2sin(2x)
So it's just -pisin(y)?

No dy/dx or anything?
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2 years ago
#4
(Original post by Dinasaurus)
So it's just -picos(y)?

No dy/dx or anything?
You haven't said what you're differentiating with respect to, but assuming it's y, then the answer would be
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2 years ago
#5
(Original post by Dinasaurus)
So it's just -pisin(y)?

No dy/dx or anything?
.
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2 years ago
#6
(Original post by B_9710)
.
Or that if you're differentiating wrt x
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Thread starter 2 years ago
#7
(Original post by B_9710)
.
Where does that dy/dx come from? What method would be used to do this or is this just something I am expected to know?
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2 years ago
#8
(Original post by Dinasaurus)
Where does that dy/dx come from? What method would be used to do this or is this just something I am expected to know?
Well
See how the dy on the top and bottom kind of cancel out leaving just d/dx (cosπy). That's what you do. Differentiate the function with respect to y then multiply by dy/dx.
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