Question 652612
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All we need are these facts:

i<sup>2</sup> = -1

(-1)<sup>ODD</sup> = -1, 

(-1)<sup>EVEN</sup> = 1 

-i<sup>6699</sup> = -(i<sup>6699</sup>) = -(i<sup>6698+1</sup>) = -(i<sup>6698</sup>i<sup>1</sup>) = -(i<sup>2·3349</sup>i<sup>1</sup>) = -(i<sup>2</sup>)<sup>3349</sup>i = -(-1)<sup>3349</sup>i = -(-1)i = i

Edwin</pre>