Math Is Fun Forum

threep14rrr

Member

From: The country I made up.

Registered: 2015-07-12

Posts: 109

-i times i

Hi!

Help! I found on mathsisfun about Imaginary Numbers that -i times i equals 1. May anyone please prove?

Thanks

-rrr

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Memorizing pi ain't no piece of PIe. You need to pray and have PIety, because it's an ePIc job.

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mathaholic

Member

From: Earth

Registered: 2012-11-29

Posts: 3,251

Re: -i times i

I believe why -i * i equals 1 is because something like this: (-1)(-1)(1)(1) which is 1*1*1 which is 1. Just an assumption.

Last edited by mathaholic (2015-07-12 23:19:01)

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Mathaholic | 10th most active poster | Maker of the 350,000th post | Person | rrr's classmate

threep14rrr

Member

From: The country I made up.

Registered: 2015-07-12

Posts: 109

Re: -i times i

Makes sense. I'll see.

Thanks!

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Memorizing pi ain't no piece of PIe. You need to pray and have PIety, because it's an ePIc job.

Progress-120

mathaholic

Member

From: Earth

Registered: 2012-11-29

Posts: 3,251

Re: -i times i

No problem. Happy to help you. I've been here for almost 3 years.

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Mathaholic | 10th most active poster | Maker of the 350,000th post | Person | rrr's classmate

threep14rrr

Member

From: The country I made up.

Registered: 2015-07-12

Posts: 109

Re: -i times i

But, does that mean -i is the answer to √1?

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Memorizing pi ain't no piece of PIe. You need to pray and have PIety, because it's an ePIc job.

Progress-120

zetafunc

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Registered: 2014-05-21

Posts: 2,436

Website

Re: -i times i

The imaginary unit is defined as i² = -1.

Help! I found on mathsisfun about Imaginary Numbers that -i times i equals 1. May anyone please prove?

(-i)*(i) = -(i*i) = -(i²) = 1.

But, does that mean -i is the answer to √1?

By convention:

√1 = 1, by convention. However, the equation x² = 1 has two solutions, 1 and -1.

threep14rrr

Member

From: The country I made up.

Registered: 2015-07-12

Posts: 109

Re: -i times i

Now I see. Thanks!

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Memorizing pi ain't no piece of PIe. You need to pray and have PIety, because it's an ePIc job.

Progress-120