Question 1029365
How can i transform {{{ 3cis(-5pi/6) }}} in to Cartesian form? (or known as rectangular form)

The problem I'm having is, How can i find the Radian Value of {{{ cos(-5pi/6)}}} and  {{{ sin(-5pi/6)}}}. Which is used to turn this polar form in to Cartesian form?

without Calculator!!
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cos(-5pi/6) = cos(5pi/6) = -sqrt(3)/2
sin(-5pi/6) = -sin(5pi/6) = -1/2
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3cis(-5pi/6) = -3sqrt(3)/2 - 3i/2
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You can't do a  Master's thesis on this.
If you're dealing with "cis" and conversions to Cartesian form, you have to know how to do this.