Inverse trig

[sfin]

Evaluate cos^-1(0.5). It is easy enough to punch in on the calculator, but my answer should be pi/3. Howq do I get this answer?

Thanks,
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[pka]

First be very sure that the calculator is set to radian mode.
Then divide that answer by pi. You should get 1/3.

On the other hand, you really should memorize the so-called ‘special angles’:
\(\displaystyle \L 0,\,\frac{\pi }{6},\,\frac{\pi }{4},\,\frac{\pi }{3},\,\frac{\pi }{2},\,\pi.\)