Home
Class 11
MATHS
4 (cos ^(3) 20^(@) + cos ^(3) 40^(@)) = ...

`4 (cos ^(3) 20^(@) + cos ^(3) 40^(@)) = 3 ( cos 20 ^(@) + cos 40^(@))`

Text Solution

AI Generated Solution

Promotional Banner

Topper's Solved these Questions

  • COMPOUND AND MULTIPLE ANGLES

    ICSE|Exercise CHEPTER TEST |23 Videos

  • COMPOUND AND MULTIPLE ANGLES

    ICSE|Exercise EXERCISE 5 (C ) |30 Videos

  • COMPLEX NUMBERS

    ICSE|Exercise Chapter Test|25 Videos

  • CONIC SECTIONS

    ICSE|Exercise Multiple Choice Questions |33 Videos

Similar Questions

Explore conceptually related problems

Prove that 4(cos ^(3) 10^(@) + sin ^(3) 20^(@)) = 3 ( cos 10^(@) + sin 20^(@)).

cos 20^(@) + cos 100^(@) + cos 140^(@) = 0

3 cos 72 ^(@) -4 sin ^(3) 18^(@) = cos 36 ^(@).

i) Prove that: cos^(3)2A+3cos2A = 4(cos^(6)A-sin^(6)A) ii) Prove that: 4(cos^(3)10^(@) + sin^(3)20^(@)) = 3(cos10^(@)+sin20^(@))

(1-cos 40^(@))/(2)=

What is the value of (cos 10 ^(@) + sin 20^(@))/( cos 20^(@) - sin 10 ^(@))?

Prove that: i) cos10^(@)cos30^(@)cos50^(@)cos70^(@)=3/16 ii) cos20^(@)cos40^(@)cos60^(@)cos80^(@)=1/16 iii) 4cos12^(@)cos48^(@)cos72^(@)=cos36^(@) iv) cos40^(@) cos80^(@)cos160^(@)=-1/8

Prove that (sin20^(@) + sin40^(@)) + (cos20^(@) + cos40^(@))=(sqrt(3)+1)cos10^(@)

Prove that cos theta + cos (120^(@) + theta) + cos ( 120^(@)-theta) =0. Hence deduce that cos ^(3) theta + cos ^(3) ( 120^(@) + theta ) + cos^3( 120^(@)-theta) = 3/4 cos 3 theta.

Prove that cos 20^(@) cos 40^(@) cos 80^(@) = (1)/(8).

ICSE-COMPOUND AND MULTIPLE ANGLES -EXERCISE 5 (D)
  1. tan 70^(@) -tan 20^(@) - 2 tan 40^(@) = 4 tan 10 ^(@).

    Text Solution

    |

  2. tan theta + 2 tan 2 theta + 4 tan 4 theta + 8 cot 8 theta = cot theta.

    Text Solution

    |

  3. 4 (cos ^(3) 20^(@) + cos ^(3) 40^(@)) = 3 ( cos 20 ^(@) + cos 40^(@))

    Text Solution

    |

  4. Prove that 4(cos ^(3) 10^(@) + sin ^(3) 20^(@)) = 3 ( cos 10^(@) + sin...

    Text Solution

    |

  5. Prove that cos ^(3) x sin ^(2) x = (1)/(16) (2cos x - cos 3x - cos 5x)...

    Text Solution

    |

  6. cot A + cot (60^(@) + A) + cot (120^(@) +A) = 3 cot 3 A.

    Text Solution

    |

  7. Prove that : cos 36 ^(@) - sin 18^(@) = (1)/(2).

    Text Solution

    |

  8. cos ^(2) 36^(@) + sin ^(2) 18^(@) = (3)/(4).

    Text Solution

    |

  9. 3 cos 72 ^(@) -4 sin ^(3) 18^(@) = cos 36 ^(@).

    Text Solution

    |

  10. cos ^(2) 48^(@) - sin ^(2) 12 ^(@) = (sqrt5+1)/(8).

    Text Solution

    |

  11. Prove that sin "" (1)/(10) pi cos ""(1)/(5) pi = (1)/(4).

    Text Solution

    |

  12. sec 72 ^(@) - sec 36^(@) = 2.

    Text Solution

    |

  13. sin ^(2) 24 ^(@) - sin ^(2) 6^(@) = (sqrt5 -1)/(8).

    Text Solution

    |

  14. sin 12 ^(@) sin 48^(@) sin 54 ^(@) = (1)/(8).

    Text Solution

    |

  15. Prove that 4 cos 6^(@) cos 42 ^(@) cos 66^(@) cos 78^(@) = (1)/(4).

    Text Solution

    |

  16. sin "" (pi)/(5) sin "" (2pi)/(5) sin ""(4pi)/(5) sin""(3pi)/(5) = (5)/...

    Text Solution

    |

  17. Prove that cos "" (2pi)/(15) cos "" (4pi)/(15) cos "" (8pi)/(15) cos "...

    Text Solution

    |

  18. cos ^(2) ""(pi)/(10) + cos ^(2) ""(2pi)/(5) + cos^(2) ""(3pi)/(5) + co...

    Text Solution

    |

  19. tan 6 ^(@) tan 42 ^(@) tan 66 ^(@) tan 78^(@) =1

    Text Solution

    |

  20. cos alpha cos 2 alpha cos 4 alpha cos 8 alpha = (1)/(16), if alpha =...

    Text Solution

    |