Express (2 + 3i)5 in the form a + ib
Question
Express (2 + 3i)5 in the form a + ib
Solution
To express (2 + 3i)^5 in the form a + ib, we first need to express the complex number in polar form.
Step 1: Convert to Polar Form A complex number z = x + yi can be expressed in polar form as z = r(cos θ + i sin θ), where r = √(x² + y²) is the magnitude and θ = atan(y/x) is the argument.
For z = 2 + 3i, we have: r = √(2² + 3²) = √13 θ = atan(3/2) = 0.9828 radians
So, z = √13(cos 0.9828 + i sin 0.9828)
Step 2: Raise to the Power Using De Moivre's theorem, (r(cos θ + i sin θ))^n = r^n(cos(nθ) + i sin(nθ))
So, (√13(cos 0.9828 + i sin 0.9828))^5 = 13^(5/2)(cos(50.9828) + i sin(50.9828))
Step 3: Convert Back to Rectangular Form We can use the identities cos θ = cos(-θ) and sin θ = -sin(-θ) to convert back to rectangular form.
a = 13^(5/2) cos(50.9828) b = 13^(5/2) sin(50.9828)
So, (2 + 3i)^5 = a + ib
Please note that the final values of a and b will depend on the exact values of cos(50.9828) and sin(50.9828), which can be calculated using a calculator.
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