Last updated at May 29, 2018 by Teachoo

Transcript

Ex 3.3, 5 Find the value of: sin 75° sin 75° = sin (45° + 30°) We know that sin (x + y) = sin x cos y + cos x sin y Hence putting x = 45° and y = 30° So, sin (45° + 30°) = sin 45° cos 30° + cos 45° sin 30° sin 75° = 1/√2 × √3/2 + 1/√2 × 1/2 = 1/√2 ( √3/2 + 1/2 ) = (√3 + 1)/(2√2) Ex 3.3, 5 Find the value of: (ii) tan 15° tan 15° = tan (45° – 30°) Using tan (x - y) = (𝑡𝑎𝑛𝑥 − 𝑡𝑎𝑛𝑦)/(1+𝑡𝑎𝑛 𝑥 𝑡𝑎𝑛𝑦 ) Here putting x = 45° and y = 30° Putting value tan (45° – 30° ) = (tan 45"°" − 〖 tan〗30"°" )/(1 + tan 45"°" tan30"°" ) tan 15° = (1 − 1/√3)/(1 + 1 × 1/√3) = ((√3 − 1" " )/√3)/((√3 + 1" " )/√3) = (√3 −1)/√3 × √3/(√3 + 1) = (√3 − 1)/(√3 + 1) Rationalizing = (√3 − 1)/(√3 + 1) × (√3 − 1)/(√3 − 1) = (√3 − 1)2/(√3 + 1)(√3 − 1) Using (a – b )2 = a2 + b2 – 2ab = ((√3)2 +(1)2 −2" " × √3 × 1)/(√3 + 1)(√3 − 1) = (3 + 1 − 2√3)/(√(3 )+ 1)(√3 − 1) Using (a – b ) (a + b) = a2 – b2 = (4 − 2√3)/((√3)2 − (1)2) = (4 − 2√3)/(3 − 1) = (4 − 2√3)/2 = (2 (2 − √(3 )))/2 = 2 – √3 Hence tan 15° = 2 – √3

Ex 3.1, 1
Important

Ex 3.1, 2 Important

Ex 3.2, 7 Important

Ex 3.2, 8 Important

Ex 3.2, 9 Important

Ex 3.3, 4 Important

Ex 3.3, 5 Important You are here

Ex 3.3, 8 Important

Ex 3.3, 11 Important

Ex 3.3, 18 Important

Ex 3.3, 23 Important

Ex 3.3, 21 Important

Example 24 Important

Ex 3.4, 4 Important

Ex 3.4, 8 Important

Ex 3.4, 9 Important

Example 27 Important

Example 28 Important

Misc 4 Important

Misc 7 Important

Class 11

Important Question for exams Class 11

- Chapter 1 Class 11 Sets
- Chapter 2 Class 11 Relations and Functions
- Chapter 3 Class 11 Trigonometric Functions
- Chapter 4 Class 11 Mathematical Induction
- Chapter 5 Class 11 Complex Numbers
- Chapter 6 Class 11 Linear Inequalities
- Chapter 7 Class 11 Permutations and Combinations
- Chapter 8 Class 11 Binomial Theorem
- Chapter 9 Class 11 Sequences and Series
- Chapter 10 Class 11 Straight Lines
- Chapter 11 Class 11 Conic Sections
- Chapter 12 Class 11 Introduction to Three Dimensional Geometry
- Chapter 13 Class 11 Limits and Derivatives
- Chapter 14 Class 11 Mathematical Reasoning
- Chapter 15 Class 11 Statistics
- Chapter 16 Class 11 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.