# core pure 2Watch

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#1
just as: sinx = [(e^ix) - (e^-ix)]/i2

does:

cosx = [(e^ix) + (e^-ix)]/2

?
0
1 week ago
#2
Yes. Google: exponential representations of trigonometric functions
1
1 week ago
#3
(Original post by FurtherMaths2020)
just as: sinx = [(e^ix) - (e^-ix)]/i2

does:

cosx = [(e^ix) + (e^-ix)]/2

?
You should be able to work this out for yourself using:

and

0
#4
(Original post by ghostwalker)
You should be able to work this out for yourself using:

and

yes, I know, but is (cosx = [(e^ix) + (e^-ix)]/2) a standard notion?
0
1 week ago
#5
(Original post by FurtherMaths2020)
yes, I know, but is (cosx = [(e^ix) + (e^-ix)]/2) a standard notion?
Well, that's not what you asked initially.

Rewriting cos x in that form and knowing it can be written in that form is certainly very useful on occasions; if that's what you mean by a "standard notion", then yes.
0
#6
(Original post by ghostwalker)
Well, that's not what you asked initially.

Rewriting cos x in that form and knowing it can be written in that form is certainly very useful on occasions; if that's what you mean by a "standard notion", then yes.
thanks
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