Stewart Calculus 8e: Section 3.
5 - Exercise 22 Page 1 of 1
Exercise 22
If g(x) + x sin g(x) = x2 , find g 0 (0).
Solution
Differentiate both sides of the given equation with respect to x.
d d 2
[g(x) + x sin g(x)] = (x )
dx dx
d d
[g(x)] + [x sin g(x)] = 2x
dx dx
0 d d
g (x) + (x) sin g(x) + x sin g(x) = 2x
dx dx
0 d
g (x) + (1) sin g(x) + x [cos g(x)] · [g(x)] = 2x
dx
g 0 (x) + sin g(x) + xg 0 (x) cos g(x) = 2x
Solve for g 0 (x).
g 0 (x)[1 + x cos g(x)] = 2x − sin g(x)
2x − sin g(x)
g 0 (x) =
1 + x cos g(x)
Evaluate it at x = 0.
2(0) − sin g(0)
g 0 (0) =
1 + (0) cos g(0)
= − sin g(0)
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