9C Homework Answers: Triangle Area, Sine and Cosine Rules | 9C 作业答案：三角形面积、正弦与余弦定理

📚 9C Homework Answers: Triangle Area, Sine and Cosine Rules | 9C 作业答案：三角形面积、正弦与余弦定理

This article provides worked solutions and explanations for the type of questions found in Exercise 9C, which focuses on the sine rule, cosine rule, and the area formula for non-right-angled triangles. Use it to check your homework, understand the methods, and prepare for exam questions.

本文提供 9C 练习中常见题型的分步答案与讲解，重点是非直角三角形的正弦定理、余弦定理和面积公式。你可以用它核对作业、理解方法并为考试题做好准备。

1. Key Formulas for Exercise 9C | 9C 练习的核心公式

Before checking individual answers, make sure you know the three core formulas used in Exercise 9C.

在核对具体答案之前，请先掌握 9C 练习中使用的三个核心公式。

Area of a triangle: A = ½ab sin C

Sine rule: a/sin A = b/sin B = c/sin C

Cosine rule: a² = b² + c² – 2bc cos A

Here, a, b and c are side lengths, and A, B and C are the angles opposite those sides. The area formula uses the included angle between sides a and b.

这里，a、b、c 是边长，A、B、C 是与这些边相对的角。面积公式使用的是边 a 和边 b 之间的夹角。

2. Worked Example 1: Finding the Area of a Triangle | 例题 1：求三角形面积

Question: Find the area of triangle ABC where side a = 8 cm, side b =

Published by TutorHao | Mathematics Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）