Find f ′ ( 0 ) if f ( x ) = sec 2 ( x ) e sin ( x ) .
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Yes, the convention method works. One could also use Chain Rule to solve this. f ( x ) = cos 2 x ⋅ e sin ( x ) = ( 1 − sin 2 x ) e sin ( x ) . Can you continue from here?
Applying y=u/v form so here u = e^sinx and v = sec^2x Derivative of u= cosxe^sinx and v = 2secx secxtanx General derivative rule of u/v is (U dv/dx -vdv/dx)/v^2 f'(x)= cosxe^sinx - 2 secx secx tandem e^sinx / sec^4x f'(0)= 1 Because e^0=1, sec0=1, tan0= 0
Quotient Rule is a specific case for Product Rule. Note that the denominator is sec 2 x = ( cos 2 x ) − 1 . It's slightly simpler to differentiate cos 2 x than sec 2 x don't you think? Furthermore, you don't have to deal with fractions anymore.
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It's actually a product rule question in disguise.
We can split f ( x ) = sec 2 x e sin x = e sin x cos 2 x into g ( x ) = e sin x and h ( x ) = cos 2 x .
Then, f ′ ( x ) = g ( x ) h ′ ( x ) + g ′ ( x ) h ( x ) by the product rule. This means we have to find g ′ ( x ) and h ′ ( x ) first. By the chain rule,
g ′ ( x ) = ( e sin x ) ′ = e sin x cos x
h ′ ( x ) = ( cos 2 x ) ′ = − 2 cos x sin x
Hence,
f ′ ( x ) = e sin x cos 3 x − 2 e sin x cos x sin x
We can then substitute in x = 0 to obtain f ′ ( 0 ) = 1 .