Trigonometric Ratio Class 11 Notes || All Trigonometric Ratios - IIT JEE | Class 11

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eSaral Academic and Editorial Team

12th June 2026

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Summary

Trigonometric ratios in Class 11 are the six ratios — sine, cosine, tangent, cosecant, secant, and cotangent — that relate the angles of a right triangle to its sides. Defined as sin θ = Perpendicular/Hypotenuse, cos θ = Base/Hypotenuse, and tan θ = Perpendicular/Base, these ratios form the foundation of trigonometry for CBSE Class 11 and JEE Main.

Trigonometric Ratio Class 11 Notes – All Ratios & Formulas

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eSaral provides detailed Notes of Physics, Chemistry, Mathematics, and Biology Notes for class 11, and 12. So here you will get class 11 notes for mathematics. There are important points in Mathematics such as formulae, equations, identities, properties, theorems, etc. what has to be remembered to solve problems in Math.eSaral is providing complete study material to prepare for IIT JEE, NEET and Board Examinations. So here Trigonometric Ratio Class 11 Notes: All Trigonometric Ratios with solved questions and answers to prepare for IIT JEE Exam With the help of Notes, candidates can plan their Strategy for a particular weaker section of the subject and study hard. So, go ahead and check the Important Notes for CBSE Class 11 Maths.

India's Best Exam Preparation for Class 11th - Download Now

Trigonometric Ratio Class 11 Notes

India's Best Exam Preparation for Class 11th - Download Now

India's Best Exam Preparation for Class 11th - Download Now

eSaral helps the students by providing them an easy way to understand concepts and attractive study material for IIT JEE, which includes the video lectures & Study Material designed by expert IITian Faculties of KOTA. eSaral provides a series of detailed chapter wise notes for all the Subjects of class 11th and 12th. These notes will also help you in your IIT JEE preparation. We hope these Mathematics Notes for Class 11 will be helpful for you to understand the important topics and help in remembering the key points from an exam point of view. Get Complete Class 11 Mathematics Notes for free video lectures and complete Course material for Class 10, JEE, and NEET Download eSaral APP. About eSaral At eSaral, we are offering a complete platform for IIT-JEE & NEET preparation. The main mission behind eSaral is to provide education to every student in India by eliminating the Geographic and Economic factors, as a nation’s progress and development depends on the availability of quality education to everyone. With the blend of education & technology, the eSaral team made the learning personalized & adaptive for everyone. eSaral Making Learning affordable, Accessible, and thoughtful for all.

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Frequently Asked Questions

What is the ASTC rule in trigonometry?

The ASTC rule tells you which trigonometric ratios are positive in each quadrant. In Quadrant I — All ratios are positive. In Quadrant II — only Sine (and cosec) are positive. In Quadrant III — only Tangent (and cot) are positive. In Quadrant IV — only Cosine (and sec) are positive. The mnemonic "All Students Take Calculus" makes it easy to remember the order.

How many trigonometric ratios are there, and what are their names?

There are exactly six trigonometric ratios: sine, cosine, tangent, cosecant, secant, and cotangent. These are grouped into three reciprocal pairs — sin/cosec, cos/sec, and tan/cot. All six are defined for any angle (not just acute angles) using the unit circle definition taught in Class 11.

What is the value of sin 45°?

The value of sin 45° is 1/√2, which is approximately 0.707. This is derived from an isosceles right triangle where both legs are equal. Equivalently, sin 45° = √2/2. This value is one of the most frequently used in JEE Main trigonometry questions.

What are the six trigonometric ratios in Class 11?

The six trigonometric ratios are sine (sin), cosine (cos), tangent (tan), cosecant (cosec), secant (sec), and cotangent (cot). For an angle θ in a right triangle, they are defined as ratios of two of the three sides: perpendicular (P), base (B), and hypotenuse (H). The primary three are sin = P/H, cos = B/H, and tan = P/B

Which trigonometric ratios are undefined and at what angles?

tan θ and sec θ are undefined when cos θ = 0, i.e., at θ = 90°, 270° (and all angles of the form 90° + 180°n). cosec θ and cot θ are undefined when sin θ = 0, i.e., at θ = 0°, 180°, 360° (and all angles of the form 180°n). These undefined points are frequently tested in JEE Main objective questions

What is the difference between sin⁻¹ θ and cosec θ?

sin⁻¹ θ (also written arcsin θ) is an inverse trigonometric function that returns an angle whose sine is θ. It is a separate topic covered later in Class 12. cosec θ is simply the reciprocal of sin θ — that is, cosec θ = 1/sin θ. The two are completely different in meaning, domain, and application

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Trigonometric Ratio Class 11 Notes || All Trigonometric Ratios - IIT JEE | Class 11

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Trigonometric Ratio Class 11 Notes

Frequently Asked Questions

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