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136 questions
Mathematics/Paper 3/Complex Numbers
CAIEA-Level9709-a · Paper 3

Complex Numbers

136 questions· page 1 of 14

Q32025 Feb/Mar·P322 partsMedium-Easy
(a)

Find two inequalities in terms of zz that define the shaded region.

(b)

Find the greatest value of z|z| for points in this region.

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Q52025 Feb/Mar·P325MMedium

The square roots of 4+65i-4 + 6\sqrt{5}i can be expressed in the Cartesian form x+iyx + iy, where xx and yy are real and exact.

By first forming a quartic equation in xx or yy, find the square roots of 4+65i-4 + 6\sqrt{5}i in exact Cartesian form.

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Q32025 May/Jun·P316MMedium

Find the complex numbers zz for which

z+5iz5\frac{z + 5i}{z - 5}

is real and z=17|z| = \sqrt{17}. Give your answers in the form z=x+iyz = x + iy, where xx and yy are real.

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Q62025 May/Jun·P313 partsMedium-Easy
(a)

State the values of ωz1\omega z_1 and ωz2\omega z_2. Give your answers in the form reiθre^{i\theta}, where r>0r > 0 and π<θπ-\pi < \theta \leq \pi.

(b)

On a sketch of an Argand diagram with origin OO, show the points A,B,CA, B, C and DD representing the complex numbers z1,z2,ωz1z_1, z_2, \omega z_1 and ωz2\omega z_2 respectively.

(c)

State the geometric effects of multiplying z1z_1 and z2z_2 by ω\omega.

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Q32025 May/Jun·P325MMedium-Easy

On an Argand diagram shade the region whose points represent complex numbers zz which satisfy both the inequalities z3i2|z - 3i| \leq 2 and 14πarg(z12i)34π\frac{1}{4}\pi \leq \arg(z - 1 - 2i) \leq \frac{3}{4}\pi.

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Q52025 May/Jun·P325MMedium

The square roots of 145i-1 - 4\sqrt{5}i can be expressed in the Cartesian form x+iyx + iy, where xx and yy are real and exact.

By first forming a quartic equation in xx or yy, find the square roots of 145i-1 - 4\sqrt{5}i in exact Cartesian form.

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Q42025 May/Jun·P332 partsMedium-Easy
(a)

It is given that z1=r1eiθ1z_1 = r_1 e^{i\theta_1} and z2=r2eiθ2z_2 = r_2 e^{i\theta_2}.

Show that (z1z2)=z1z2(z_1 z_2)^* = z_1^* z_2^*.

(b)

z=3e14πiz = 3e^{\frac{1}{4}\pi i} is a root of the equation z2+bz+c=0z^2 + bz + c = 0, where bb and cc are real.

State the other root and hence find the values of bb and cc.

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Q62025 May/Jun·P336MMedium-Hard

Find the complex numbers zz for which z+4z+4i\frac{z + 4}{z + 4i} is real and z=10|z| = \sqrt{10}. Give your answers in the form z=x+iyz = x + iy, where xx and yy are real.

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Q32025 May/Jun·P352 partsMedium-Easy
(a)

Express st\frac{s}{t} in the form reiθr\text{e}^{\text{i}\theta}, where π<θπ-\pi < \theta \leq \pi and r>0r > 0.

(b)

In an Argand diagram with origin OO, the points AA and BB represent the complex numbers ss and st\frac{s}{t} respectively.

By considering the line segments OAOA and OBOB, or otherwise, state the two geometric effects of dividing a complex number by 6e3i6\text{e}^{3\text{i}}.

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Q52025 May/Jun·P352 partsMedium-Easy
(a)

For the points on this locus, determine the maximum and minimum possible values of z|z|.

(b)

For the points on this locus, determine the minimum possible value of argz\arg z.

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