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Mathematics 15 Online
OpenStudy (anonymous):

any idea on how to solve this?

OpenStudy (anonymous):

\[(\frac{ i^3 }{ 3 })^3\]

hartnn (hartnn):

\(\huge (\frac{a}{b})^x=\frac{a^x}{b^x} \\ (a^b)^c=a^{bc}\)

hartnn (hartnn):

\(\huge (\frac{ i^3 }{ 3 })^3=\frac{(i^3)^3}{3^3}=?\)

OpenStudy (anonymous):

that would be i^9/27 ?\[\frac{ i^9 }{ 27 }\]

hartnn (hartnn):

yup, thats correct :) now is 'i' just a variable here or square root of -1 ??

OpenStudy (anonymous):

its a square root of -1

hartnn (hartnn):

so u know what is i^2 ?

OpenStudy (anonymous):

its -1

hartnn (hartnn):

and i^3 = ?

hartnn (hartnn):

and i^4 = ?

OpenStudy (anonymous):

1^3 = -i i^4 = 1

hartnn (hartnn):

now we write i^9 as i*(i^4)^2 got this ?

OpenStudy (anonymous):

so it would be a -i ?

hartnn (hartnn):

why - *minus* ?

OpenStudy (anonymous):

as in -i/27

hartnn (hartnn):

i^4 =+1 its square = +1 1*i=i

hartnn (hartnn):

so it would be i/27

OpenStudy (anonymous):

ohhh well its because i thought that i to the power of an odd number ( i.e., i^9 ) would equal a negative i

hartnn (hartnn):

now u got it ?

hartnn (hartnn):

i mean any more doubts ?

OpenStudy (anonymous):

yeah, so is there no such thing as a -i ?

hartnn (hartnn):

yes it it, i^-1 = -i i^3 = -i i^7 = -i i^11= -i i^15 =-i .... did u get the pattern ?

OpenStudy (anonymous):

umm i think. not too sure.

hartnn (hartnn):

after every 4th power, the value gets repeated, like i^0 = i^4 = i^8 = i^12 =.... = 1 i^1 = i^ 5 = i^9 =.....=i and so on. ok ?

OpenStudy (anonymous):

okay yeah thats what i thought, i just didnt want to sound dumb lol thanks!

hartnn (hartnn):

welcome :)

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