Homework Help: Trigonometry

Posted by Anonymous on Tuesday, August 7, 2012 at 5:09pm.

Given the rectangular-form point (–1, 4), which of the following is an approximate primary
representation in polar form?
A. −(4.12, 1.82)
B. (−4.12, −1.33)
C. (4.12, 1.82)
D. (4.12, 4.96)

Change 8 cis 240degrees to rectangular form.

A. -4(Square root 3)-4i
B. -8(Square root 3)-8i
C. -4-4(Square root 3i)
D. -8-8(Square root 3i)

Trigonometry - Reiny, Tuesday, August 7, 2012 at 7:05pm
(-1,4) is in quadrant II
tan^-1 Ų = -4
Ų = 104° or 1.82 radians
the length of r is √(1+16) = √17 = appr 4.12

mmmmhhhh? Can you do something with that?

8 cis 240°
= 8(cos240° + isin240°)
= 8(-1/2 + i(-√3/2)
= -4 - 4√3 i

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