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    Hello guys I'm trying to differentiate a parametric equation which i attached you here but there's a part i don't understand when it comes down to differentiate y=2tcost and how it was differentiated . i know that differentiation of cos t= -sin t hence dy/dt of y=2tcost should be given as -2tsint am i missing something here?
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    (Original post by Alen.m)
    Hello guys I'm trying to differentiate a parametric equation which i attached you here but there's a part i don't understand when it comes down to differentiate y=2tcost and how it was differentiated . i know that differentiation of cos t= -sin t hence dy/dt of y=2tcost should be given as -2tsint am i missing something here?
    You need to use the product rule since t is a variable. \frac{d}{dt} (2t \cos t) \neq 2t \frac{d}{dt}(\sin t)
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    (Original post by Alen.m)
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    Surely you wouldn't agree with be saying \frac{d}{dx} (x \cdot x) = x \frac{d}{dx} (x) = x \cdot 1 = x, riiiight?
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    (Original post by Zacken)
    Surely you wouldn't agree with be saying \frac{d}{dx} (x \cdot x) = x \frac{d}{dx} (x) = x \cdot 1 = x, riiiight?
    course not )) so basically when there are two functions multiplies together we use product rule
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    (Original post by Alen.m)
    course not )) so basically when there are two functions multiplies together we use product rule
    Yes.
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    (Original post by Zacken)
    Yes.
    thanks
 
 
 
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