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Maths Question 8 – AP-EAMCET 2026

If z1=3+i3 and z2=3+i, then the complex number (z1z2)50 lies in the

It is generally easier to perform multiplication, division, and exponentiation of complex numbers when they are in polar form. Convert z1 and z2 to their polar forms first.

Step 1: Convert z1 and z2 to Polar Form✦ Active

First, convert the given complex numbers z1 and z2 into their polar forms, r(cosθ+isinθ), where r is the modulus and θ is the argument.

z1=3+i3 |z1|=(3)2+(3)2=3+3=6 arg(z1)=tan1(33)=tan1(1)=π4 z1=6(cosπ4+isinπ4) z2=3+i |z2|=(3)2+(1)2=3+1=4=2 arg(z2)=tan1(13)=π6 z2=2(cosπ6+isinπ6)
💡 Teacher's Secret Hint

Always ensure the argument θ is in the correct quadrant based on the signs of the real and imaginary parts of the complex number.

Step 2: Calculate the Quotient z1z2 in Polar Form○ Expand

Use the property for division of complex numbers in polar form: r1(cosθ1+isinθ1)r2(cosθ2+isinθ2)=r1r2(cos(θ1θ2)+isin(θ1θ2)). Calculate the difference of the arguments:

z1z2=62(cos(π4π6)+isin(π4π6)) π4π6=3π2π12=π12 z1z2=62(cosπ12+isinπ12)
💡 Teacher's Secret Hint

Remember that when dividing complex numbers, you divide the moduli and subtract the arguments.

Step 3: Apply De Moivre's Theorem to find (z1z2)50○ Expand

Now, apply De Moivre's Theorem to raise the complex number to the power of 50. The modulus will be raised to the power of 50, and the argument will be multiplied by 50.

(z1z2)50=(62)50(cos(50π12)+isin(50π12)) Simplify the argument: 50π12=25π6 (z1z2)50=(62)50(cos(25π6)+isin(25π6))
💡 Teacher's Secret Hint

The modulus (62)50 is a positive real number and only affects the distance from the origin, not the quadrant. The quadrant is determined solely by the argument.

Step 4: Determine the Quadrant○ Expand

To determine the quadrant, we need to find the principal value of the argument 25π6. We can do this by subtracting multiples of 2π until the angle lies in the interval [0,2π).

25π6=24π+π6=4π+π6 Since 4π represents two full rotations, the effective argument is π6. The angle θ=π6 satisfies 0<θ<π2.

Therefore, the complex number (z1z2)50 lies in the First Quadrant.

💡 Teacher's Secret Hint

Angles in the first quadrant are between 0 and π/2 radians (or 0 and 90). Angles in the second quadrant are between π/2 and π, third between π and 3π/2, and fourth between 3π/2 and 2π.

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