Home
Class 11
MATHS
cos20^(@).cos40^(@).cos60^(@).cos80^(@)=...

`cos20^(@).cos40^(@).cos60^(@).cos80^(@)=1/16`

Text Solution

Verified by Experts

The correct Answer is:
`=1/16=R.H.S`
NA
Promotional Banner

Topper's Solved these Questions

  • TRIGONOMETRY

    SUBHASH PUBLICATION|Exercise Alternate Methods|12 Videos

  • SUPER MODEL QUESTION PAPER-3

    SUBHASH PUBLICATION|Exercise Point E|4 Videos

Similar Questions

Explore conceptually related problems

cos130^(@)+cos110^(@)+cos10^(@)=0

cos130^(@)+cos110^(@)+cos10^(@)=0

Prove that cos 20^@ cos 40^@ cos 60^@ cos 80^@=1/16 .

Evaluate cos1^(@)cos 2^(@)cos3^(@)cos4^(@)...cos179^(@)cos 188 .

Find x:sin 2x = sin 60^(@) cos 30^(@) - cos 60^(@) sin 30^(@) .

Evaluate: sec 50^(@) sin 40^(@)+cos 40^(@) cosec 50^(@) .

Find the value of cos60^(@) cos 30^(@)-sin 60^(@) sin 30^(@)

Is it right to say that cos ( 60^(@) + 30 ^(@) ) = cos 60^(@) cos 30 ^(@) -sin 60^(@) sin 30 ^(@)

If sin x = sin 60^(@) cos 30^(@)- cos 60^(@) sin 30^(@) , then the value of x is

cos 20^(circ) cos 40^(circ) cos 60^(circ) cos 80^(circ)=

SUBHASH PUBLICATION-TRIGONOMETRY-Prove the following
  1. (cos 75^(@)+cos15^(@))/(sin75^(@)-sin 15^(@))=sqrt(3)

    Text Solution

    |

  2. (sin6A+sin2A+2sin4A)/(sin7A+sin3A+2sin5A)=(sin4A)/(sin5A)

    Text Solution

    |

  3. Prove that : cosA+cos(120^(@)-A)+cos(120^(@)+A)=0

    Text Solution

    |

  4. cos^(2)theta+cos^(2)(60^(@)+theta)+cos^(2)(60^(@)-theta)=3/2

    Text Solution

    |

  5. Show that:4sinA.sin(60^(@)+A)sin(60^(@)-A)=sin3A

    Text Solution

    |

  6. If A+B+C=pi, Prove that tanA+tanB+tanC=tanA.tanB.tanC

    Text Solution

    |

  7. cos20^(@).cos40^(@).cos60^(@).cos80^(@)=1/16

    Text Solution

    |

  8. If A+B+C=pi prove that "tan"A/2"tan"B/2+"tan"B/2"tan"C/2+"tan"C/2"tan"...

    Text Solution

    |

  9. If A+B+C=pi, prove that sin 2A+sin 2B+sin 2C=4 sinA sin B sinC.

    Text Solution

    |

  10. Prove that: sinA+sinB+sinC=4cos(A/2)cos(B/2)cos(C/2) if A + B +C =180 ...

    Text Solution

    |

  11. cos^(2)A+cos^(2)B-cos^(2)C=1-2sinA sinB cosC

    Text Solution

    |

  12. In DeltaABC, prove that (sin(B-C))/(sin(B+C))=(b^(2)-c^(2))/(a^(2))

    Text Solution

    |

  13. (a^(2)-b^(2))/(c^(2)-a^(2))=c/b . (sin(A-B))/(sin(C-A))

    Text Solution

    |

  14. (cos2A)/(a^(2))-(cos2B)/(b^(2))=1/(a^(2))-1/(b^(2))

    Text Solution

    |

  15. Sigmaa sin (B-C)=0

    Text Solution

    |

  16. If a sin a=b sin B then prove that Delta ABC is isosceles.

    Text Solution

    |

  17. If a cosA=b cos B then prove that Delta ABC is eitherisosceles or righ...

    Text Solution

    |

  18. In DeltaABC if (cosA)/a=(cosB)/b=(cosC)/c Prove that DeltaAB C is equi...

    Text Solution

    |

  19. Prove that a^(2)+b^(2)+c^(2)=2(ab cos C +bc cosA +ca cos B)

    Text Solution

    |

  20. (cosA)/a+(cosB)/b+(cosC)/c=(a^(2)+b^(2)+c^(2))/(2abc)

    Text Solution

    |