Question

What is `sin^-1 -1`?

Answer 1

As the interval is not specified, the general solution is given.
`( 2n-1/2)pi, n=0, +-1, +-2, +-3,...`.
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Explanation:

Sine is negative in the 3rd and 4th quadrant. The odd multiple of #pi/2) here is the solution.

Answer: `( 2n-1/2)pi, n=0, +-1, +-2, +-3, .`.
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n = 1 gives `(3/2)pi`.