Suppose that:
( 2 + i 3 2 ) ( 1 + i ) = α + i β
where, α and β are real numbers and i 2 = − 1 . Find ⌊ 1 0 0 0 α ⌋ + ⌊ 1 0 0 0 β ⌋ , where ⌊ x ⌋ is the greatest integer function.
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First we write ( 2 + i 3 2 ) in form k ( cos a + i sin a ) .
X = ( 2 + i 3 2 ) 1 + i = ( 3 2 5 ) 1 + i ( 2 3 5 2 + i 1 0 1 ) 1 + i
Now we can write both ( 3 2 5 ) and ( 2 3 5 2 + i 1 0 1 ) in their exponential form. By separating real and imaginary numbers in exponent we can get one purely real number and one complex.
X = e ( 1 + i ) ln 3 2 5 e ( 1 + i ) i arcsin 1 0 1 = e ln 3 2 5 − arcsin 1 0 1 e i ( ln 3 2 5 + arcsin 1 0 1 )
This can easily be transformed to the form of α + i β .
X = e ln 3 2 5 − arcsin 1 0 1 [ cos ( ln 3 2 5 + arcsin 1 0 1 ) + i sin ( ln 3 2 5 + arcsin 1 0 1 ) ]
α = e ln 3 2 5 − arcsin 1 0 1 cos ( ln 3 2 5 + arcsin 1 0 1 ) ≈ 0 , 8 1 1 6 7 4
β = e ln 3 2 5 − arcsin 1 0 1 sin ( ln 3 2 5 + arcsin 1 0 1 ) ≈ 0 , 7 1 3 3 3 7
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Let x be that expression, so using the exponential function we have:
x = e ( 1 + i ) ln ( 2 + i 3 2 )
Now, use the formula for the principal logarithm of a complex number:
ln ( z ) = ln ( ∣ z ∣ ) + i arg ( z ) ln ( 2 + i 3 2 ) = ln ( 3 2 5 ) + i arctan ( 3 1 )
So, we have now:
x = e ( 1 + i ) ( ln ( 3 2 5 ) + i arctan ( 3 1 ) )
Expand:
x = e ln ( 3 2 5 ) − arctan ( 3 1 ) + i ( ln ( 3 2 5 ) + arctan ( 3 1 ) ) x = e ln ( 3 2 5 ) − arctan ( 3 1 ) [ cos ( ln ( 3 2 5 ) + arctan ( 3 1 ) ) + i sin ( ln ( 3 2 5 ) + arctan ( 3 1 ) ) ]
To evaluate that expression, we need to use radians:
x ≈ 1 . 0 8 0 5 8 5 7 9 1 5 9 ( 0 . 7 5 1 1 4 3 0 6 2 4 1 + 0 . 6 6 0 1 3 9 4 5 4 8 i ) x ≈ 0 . 8 1 1 6 7 4 5 2 0 6 9 + 0 . 7 1 3 3 3 7 3 1 5 3 2 i
Comparing we get ⌊ 1 0 0 0 α ⌋ = 8 1 1 and ⌊ 1 0 0 0 β ⌋ = 7 1 3 , so the final answer is 8 1 1 + 7 1 3 = 1 5 2 4 .