Q. 2.) evaluate the cross ratio (2,1+i,1,1+i) b) identify the points where the mapping f(z)=21∗(z+z1) is conformal.
Calculate Cross Ratio: Calculate the cross ratio for the points 2, 1+i, 1, and 1+i using the formula (z1−z3)(z2−z4)/(z1−z4)(z2−z3).Cross ratio = (2−1)(1+i−1+i)/(2−1+i)(1+i−1)
Simplify Numerator and Denominator: Simplify the numerator and the denominator.Cross ratio = (1)(2i)/(1+i)(i)
Multiply to Eliminate Complex Number: Multiply the numerator and denominator to get rid of the complex number in the denominator.Cross ratio = (2i)/(i2+i)
Simplify i2 and Continue: Simplify i2 to −1 and continue simplifying.Cross ratio = (2i)/(−1+i)
Multiply by Conjugate: Multiply the numerator and denominator by the conjugate of the denominator to make the denominator real.Cross ratio = (2i)(−1−i)/((−1+i)(−1−i))
Perform Multiplication: Perform the multiplication in the numerator and the denominator.Cross ratio = (1−i2)(−2i−2i2)
Combine Like Terms: Simplify i2 to −1 in the numerator and denominator.Cross ratio = (−2i+2)/(1+1)
Divide by Denominator: Combine like terms and simplify the denominator.Cross ratio = (2−2i)/2
Identify Conformal Points: Divide both terms in the numerator by the denominator.Cross ratio = 1−i
Set Derivative Equal to Zero: Now, identify the points where the mapping f(z)=21⋅(z+z1) is conformal. Conformal mappings preserve angles, so we need to find where the derivative of f(z) does not equal zero or infinity. f′(z)=21⋅(1−z21)
Simplify by Multiplying: Set the derivative equal to zero to find where the mapping is not conformal.0=21×(1−z21)
Add z21: Multiply both sides by 2 to simplify.0=1−z21
Take Square Root: Add 1/z2 to both sides.1/z2=1
Solve for z: Take the square root of both sides.z1=±1
Mapping Not Conformal: Take the reciprocal to solve for z.z=±1
Mapping Not Conformal: Take the reciprocal to solve for z. z=±1 The mapping is not conformal at z=±1.
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