homework help trig please!?

give answers to these calculations in trigonometric form:

(a) 12(cos(65degree)=isin(65degree)) / 9(cos(24degree)+isin(24degree))

(b) 2(cos(pi/6)+isin(pi/6))x 4(cos(pi/3)+isin(pi/3))

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  • 8 years ago
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    I'll start with (b):

    2(cos(pi/6) + isin(pi/6)) = 2e^(i pi/6)

    and

    4(cos(pi/3) + isin(pi/3)) = 4e^(i pi/3)

    When you multiply them together you get

    8e^(ipi/6+i pi/3) = 8e^(i pi/2)

    = 8(cos(pi/2) + i sin(pi/2)) = 8(0+i) = 8i.

    My problem with (a) is that I think the "=" sign is supposed to be a plus sign. (???)

    Then you have

    12 e^(13 i pi/36) / 9 e^(2 i pi/15)...the exponents will be subtracted...

    = (4/3) e^(41 i pi/180)

    = (4/3) ( cos(41 degrees) + i sin(41 degrees) )

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