#### Question

# Convert ( 1.5 cis 0.55)^-1 to standard (a+bi) form please?

Hello

What I tried was using De Moivre's formula.

so

(1.5 cis 0.55)^-1

=

1.5^-1 cis -1* 0.55

but this gives me the answer

0.66 - 0.55 i

but the correct answer is something like

0.57 - 0.34 i

Thank you :)

#### Answers

That's the correct method. Did you happen to forget to switch to radians?

Because:

(1.5 cis 0.55)^(-1)

= (1.5)^(-1) * cis(-1 * 0.55)

= (cos 0.55 + i sin 0.55)/1.5

≈ 0.57 + 0.35i.

I hope this helps!

#1

=(1.5ciso.55)^-1

=(1.5^-1)(coso.55-isino.55) solve with calci

=o.57-o.34 i ans

#2

Glad you got it, though!

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#3

I forgot to pull out the negative from sine. 'doh!

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#4