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What is the rectangular form(a + bi) of:


1. 5 cis(255°)

2. sqrt3 cis (11pi/6)

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2 answers

  1. 5 cis(255°)
    = 5(cos255° + i sin255) , note that 225 is (180 + 45)° , quadrant III
    thus cos 225 = -cos45 = -√2/2
    and sin 225 = -sin45 = -√2/2

    5cis225
    = 5(-√2/2 - √2/2 i)
    = -5√2/2 - 5√2/2 i

    for the second, 11π/6 is a multiple of π/6 , (or 30°)
    so follow my procedure

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  2. hmmm. is 255 a typo for 225? Probably.

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