Class 10 Trigonometry Lecture 4 | Trigonometric Identities Theory Basic PYQs | CBSE 2027 | By Bhaiya

Welcome to Lecture 4 of the Class 10 Trigonometry series! 🎯 In this lecture, we learn the three most important Trigonometric Identities, understand where they come from using the Pythagoras theorem, and then apply them to basic questions and Previous Year Questions (PYQs). Identities are the backbone of trigonometry, and they appear every year in the CBSE Board Exam. 📚 What you’ll learn in this lecture: 🔹 What a trigonometric identity is 🔹 Proof of sin²θ + cos²θ = 1 using Pythagoras theorem 🔹 1 + tan²θ = sec²θ (i.e. 1/cos²θ) 🔹 1 + cot²θ = cosec²θ (i.e. 1/sin²θ) 🔹 Different forms of each identity (e.g. sin²θ = 1 − cos²θ, sec²θ − tan²θ = 1) 🔹 Important trigonometric formulas and reciprocal relations 🔹 How to express all ratios in terms of one ratio 🔹 Basic questions and PYQ practice 🔹 Step-by-step method to prove identities in the exam 📝 Types of PYQs solved in this lecture: ✔️ Find the value of: 9sec²A − 9tan²A ✔️ Prove: (1 + tan²A)(1 − sin A)(1 + sin A) = 1 ✔️ Prove: (sec A + tan A)(1 − sin A) = cos A ✔️ Prove: (1 − cos²A) cosec²A = 1 ✔️ Prove: cos A / (1 + sin A) + (1 + sin A) / cos A = 2 sec A ✔️ Express sin A, sec A and tan A in terms of cot A ✔️ MCQs and short-answer questions based on identities 💡 Tip: Write all three identities and their different forms on one page and revise them daily. Most identity questions become easy once you can spot which form to use. 👨‍🎓 Who should watch: CBSE Class 10 students preparing for Boards 2027 Students who find proving identities difficult Anyone who wants to practise basic identity-based PYQs 📌 Watch the series in order: ▶️ Lecture 1: Introduction to Trigonometry ▶️ Lecture 2: Question Practice Session ▶️ Lecture 3: Standard Angles Values + PYQs ▶️ Lecture 4: Trigonometric Identities Theory + Basic PYQs (this video) ⏱️ Timestamps: 00:05– Different forms of identities 2:04 – Basic questions 18:00 – Previous Year Questions (PYQs) 🔔 Don’t forget to: 👍 Like the video if it helped you 💬 Comment your doubts. Bhaiya will answer them! 📤 Share with friends preparing for boards 🔔 Subscribe and turn on notifications for the next lecture Let’s Ace Trigonometry! Practice → Solve → Score High! 😊 #Class10Maths #Trigonometry #TrigonometricIdentities #CBSE2027 #Class10Trigonometry #BoardExam2027 #MathsByBhaiya #PYQ #CBSEClass10 #TrigonometryIdentities #ProveIdentities