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CIE 9709 2022 March Paper 32 Q2

A Level / CIE / P3

CIE 9709 2022 March Paper 32 Paper · Question 2

题目

Problem

On a sketch of an Argand diagram, shade the region whose points represent complex numbers zz satisfying the inequalities ∣z+2−3i∣≤2|z+2-3\mathrm{i}|\leq2 and arg⁡z≤34π\arg z\leq\frac34\pi.

(4)
题目中文翻译

在阿根图的草图上,用阴影表示满足不等式 ∣z+2−3i∣≤2|z+2-3\mathrm{i}|\leq2 和 arg⁡z≤34π\arg z\leq\frac34\pi 的复数 zz 所对应的点组成的区域。

(4)
原卷通用作答要求

Answer all questions. You should use a calculator where appropriate.

You must show all necessary working clearly; no marks will be given for unsupported answers from a calculator.

Give non-exact numerical answers correct to 3 significant figures, or 1 decimal place for angles in degrees, unless a different level of accuracy is specified in the question.

请回答所有题目。适当时应使用计算器。必须清楚展示所有必要的计算过程;仅给出计算器答案而没有过程,不予评分。除非题目另有精度要求,非精确数值答案保留 3 位有效数字,以度为单位的角度保留 1 位小数。

解答

解法一

思路

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模条件给出圆心 (−2,3)(-2,3)、半径 22 的闭圆盘。整个圆盘在上半平面,辐角条件因此选择射线 y=−xy=-x 的顺时针一侧。

答题过程

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Write z=x+yiz=x+y\mathrm{i}. The first condition gives

(x+2)2+(y−3)2≤4.(x+2)^2+(y-3)^2\le4.

Draw this circle, with centre (−2,3)(-2,3) and radius 22.

The boundary arg⁡z=3π/4\arg z=3\pi/4 is the ray from the origin through the second quadrant along y=−xy=-x.

The disc lies entirely above the real axis. Therefore the condition arg⁡z≤3π/4\arg z\le3\pi/4 selects points with y≥−xy\ge-x. Shade the intersection of this half-plane and the disc, including both boundaries.