1. Chapter 3 Class 11 Trigonometric Functions
  2. Serial order wise
  3. Ex 3.3

Ex 3.3, 6 - Chapter 3 Class 11 Trigonometric Functions

Last updated at May 29, 2018 by

Ex 3.3, 6 - Prove that cos (pi/4 - x) cos (pi/4 - y) - Chapter 3 - (x + y) formula

  1. Chapter 3 Class 11 Trigonometric Functions
  2. Serial order wise

    3. Ex 3.3

    Ex 3.4 →

Transcript

Ex 3.3, 6 Prove that: cos ( /4 ) cos ( /4 ) sin ( /4 ) sin ( /4 ) = sin ( + ) Taking L.H.S We know that cos (A + B) = cos A cos B sin A sin B The equation given in Question is of this form Hence A = ( /4 ) B = ( /4 ) Hence cos ( /4 ) cos ( /4 ) sin ( /4 ) sin ( /4 ) = cos [( /4 )" " +( /4 )] = cos [ /4 + /4 ] = cos [ /4+ /4 ] = cos [ /2 ( + ) ] Putting = 180 = cos [(180 )/2 ( + ) ] = cos [90 ( + ) ] = sin ( + ) = R.H.S Hence proved

Chapter 3 Class 11 Trigonometric Functions
Serial order wise

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
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.