Derivatives: Chain Rule
For p(x) = m[n(x)] = m o n:
p'(x) = m'[n(x)]n'(x)
Example #1:
Find the derivative of (x−1/2)3 using the Chain Rule.
Solution #1:
Using Chain Rule with n(x) = x−1/2 and m(x) = x3 it follows that
n'(x) = (−½)x−3/2
and
m'[n(x)] = 3(x−1/2)2 = 3x−1
p'(x) = m' [n(x)]n'(x) = 3x−1(−½)x−3/2
n'(x) = (−½)x−3/2
and
m'[n(x)] = 3(x−1/2)2 = 3x−1
p'(x) = m' [n(x)]n'(x) = 3x−1(−½)x−3/2
p'(x) = (−3/2)x−5/2
Example #2:
Find the derivative of sin (1 + x2) using the Chain Rule.
Solution #2:
Using Chain Rule with n(x) = 1 + x2 and m(x) = sin x it follows that
n'(x) = 2x
and
m'[n(x)] = cos(1 + x2)
n'(x) = 2x
and
m'[n(x)] = cos(1 + x2)
p'(x) = m' [n(x)]n'(x) = cos(1 + x2)2x
p'(x) = 2x cos(1 + x2)
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