※ 引述《GLP (^__________^)》之銘言:
tan(x-y)= (tan x - tan y) / ( 1 + tan x tan y )
tan(x+y)= (tan x + tan y) / ( 1 - tan x tan y )
|x-iy|= √(x^2 + y^2 )
|x+iy|= √(x^2 + y^2 )
由 e^iθ = cosθ + i sinθ,
e^(-iθ) = cos(-θ) + i sin(-θ) = cosθ - i sinθ
|e^iθ| = |e^(-iθ)| = 1
-iΘ 2
|e | = 1
iΘ 2
|e | = 1
iΘ 2 | |2 2 2
|x-ye | = | x - ycosθ- i ysinθ | = (x-ycosθ) + (ysinθ)
| |
2 2
= x + y - 2ycosθ
iΘ 2 2 2
|x+ye | = x + y + 2ycosθ
-iΘ 2 | |2 2 2
|x-ye | = | x - ycosθ- i ysinθ | = (x-ycosθ) + (ysinθ)
| |
2 2
= x + y - 2ycosθ
-iΘ 2 | |2 2 2
|x+ye | = | x + ycosθ - i ysinθ | = x + y + 2ycosθ
| |
iΘ -iΘ 3 3 3
(e - e ) = ( 2 cosθ ) = 8 cos θ
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rehearttw 許老師(Reheart-易懷),愛生公式,愛胡思亂想
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