Derivatives of Inverse Trigs via Implicit Differentiation
We can use implicit differentiation to find derivatives of inverse
functions. Recall that the equation y=f−1(x) means the same things as
x=f(y).
Taking derivatives of both sides gives
1=f′(y)dydx.
Dividing both sides by f′(y) (and swapping sides) gives
dydx=1f′(y).
Once we rewrite f′(y) in terms of
x, we have the derivative of f−1(x).
In the following video, we use this trick to differentiate
the inverse trig functions sin−1, cos−1 and tan−1.
The end results are
dsin−1(x)dx=1√1−x2,dcos−1(x)dx=−1√1−x2,dtan−1(x)dx=11+x2.
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