## Revision Notes for ICSE Class 9 Mathematics Chapter 23 - Free PDF Download

## FAQs on ICSE Class 9 Math Revision Notes Chapter 23 - Trigonometrical Ratios of Standard Angles

**1. What is trigonometry, according to chapter 23 of Class 9 ICSE Maths?**

Trigonometry is a section of mathematics in geography, which handles the sides and angles of a right-angled triangle. Trigonometric ratios are assessed with the sides and angles. For any trigonometry-related queries of Class 9 ICSE maths, head over to the website of Vedantu. Here, you can find all the reading materials that will enhance your understanding of the chapter and further, help you to make the basics of the chapter strong.

**2. What are the trigonometric ratios according to chapter 23 of Class 9 ICSE Maths?**

The names and abbreviations of trigonometric ratios are sine (sin), secant (sec), cosine (cos), cosecant (cosec), cotangent (cot) and tangent (tan). The standard angles for these trigonometric ratios are 0°, 30°, 45°, 60° and 90°. These angles can also be depicted as radians which are 0, π/2, π/3, π/4, π/6.

**3. According to chapter 23 of Class 9 ICSE Maths, where are trigonometric ratios used?**

The trigonometric ratios can be applied to find numerous pieces of information which are concerned with specific functions of angles and their application to calculations, and one of their main motives is to help figure out triangles. A triangle can be solved by finding the measures of all the angles and the lengths of the sides.

**4. When can we use sine law, according to chapter 23 of Class 9 ICSE Maths?**

The sine rule is applied when we have either a) two angles and one side, or b) two sides and a non-included angle. The cosine rule is applied when having either a) three sides or b) two sides and the included angle. Download the Vedantu app for any queries that you have regarding the chapter. You can sign up for free classes wih our experts as well for a proper grasp of the concepts.

**5. According to chapter 23 of Class 9 ICSE Maths, how do you find a hypotenuse?**

The hypotenuse is known as the longest side of a right-angled triangle. To figure out the longest side we apply the hypotenuse formula that can be easily driven from the Pythagoras theorem, (Hypotenuse)2 = (Base)2 + (Altitude)2. Hypotenuse formula = √((base)2 + (height)2) (or) c = √(a2 + b2).