Home
Class 11
MATHS
Prove that: cos(pi/7)cos((2pi)/7)cos((4p...

Prove that: `cos(pi/7)cos((2pi)/7)cos((4pi)/7)=-1/8`

Text Solution

AI Generated Solution

Promotional Banner

Topper's Solved these Questions

  • TRIGONOMETRIC RATIOS OF COMPOUND ANGLES

    RD SHARMA ENGLISH|Exercise All Questions|149 Videos

Similar Questions

Explore conceptually related problems

Prove that : cos(pi/7)cos((2pi)/7) cos((3pi)/7)=1/8

Prove that: cos(pi/5)cos((2pi)/5)cos((4pi)/5)cos((8pi)/5)=(-1)/16

3.Prove that (i) "cos((2pi)/7)*cos((4pi)/7)*cos((8pi)/7)=1/8

Prove that 4cos((2pi)/7).cos(pi/7)-1=2cos((2pi)/7) .

Prove that: cos^4(pi/8)+cos^4((3pi)/8)+cos^4((5pi)/8)+cos^4((7pi)/8)=3/2

Prove that: sin((4pi)/9+7)cos(pi/9+7)-cos((4pi)/9+7)sin("pi/9+7)=(sqrt(3))/2

Prove that cos ((2pi)/7)+ cos ((4pi)/7) + cos ((6pi)/7) = - 1/2

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((14pi)/(15))=1/(16)

Prove that cos((2pi)/(15))cos((4pi)/(15))cos((8pi)/(15))cos((16pi)/(15))=1/(16)

Show that cos(pi/65)cos((2pi)/65)cos((4pi)/65)cos((8pi)/65)cos((16pi)/65)cos((32pi)/65)=1/64

RD SHARMA ENGLISH-TRIGONOMETRIC RATIOS OF MULTIPLE AND SUBMULTIPLE ANGLES-All Questions
  1. Prove that: (1+sec2theta)(1+sec4theta)(1+sec8theta)....(1+sec2^ntheta)...

    Text Solution

    |

  2. If theta=pi/(2^n+1) , prove that: 2^ncosthetacos2thetacos2^2 cos2^(n-1...

    Text Solution

    |

  3. Prove that: cos(pi/7)cos((2pi)/7)cos((4pi)/7)=-1/8

    Text Solution

    |

  4. If alpha and beta are distinct roots of acostheta+b sintheta=c , prove...

    Text Solution

    |

  5. Prove that: sin^2(A/2+pi/8) - sin^2(A/2-pi/8)= 1/sqrt(2)sinA

    Text Solution

    |

  6. Prove that: Sin 4A = 4 cos^3 A sin A - 4 sin^3 A cos A

    Text Solution

    |

  7. If tanA=1/7a n d tanB=1/3 , show that cos2A=sin4Bdot

    Text Solution

    |

  8. If 2t a nalpha/2=tan(beta/2) , prove that cosalpha=(3+5cosbeta)/(5+3c...

    Text Solution

    |

  9. If acos2theta+bsin2theta= c, alpha and beta as its roots , then prove ...

    Text Solution

    |

  10. If cosalpha+cosbeta=0=s inalpha+s inbeta, then prove that cos2alpha+co...

    Text Solution

    |

  11. Prove that: 15sin(5pi)/(12)+15cos(5pi)/(12)-20sin^3(5pi)/(12)-20cos(5p...

    Text Solution

    |

  12. Prove that: sin(pi/5)sin( (2pi)/5)sin(3pi/5)sin(4pi/5)=5/(16)

    Text Solution

    |

  13. Find general solution of the trigonometric equation sin5theta =1

    Text Solution

    |

  14. Prove that: sin^4(pi/8)+sin^4((3pi)/8)+sin^4((5pi)/8)+sin^4((7pi)/8)=...

    Text Solution

    |

  15. Prove that: cos^4pi/8+cos^4(3pi)/8+cos^4(5pi)/8+cos^4(7pi)/8=3/2

    Text Solution

    |

  16. Prove that:tan6^0tan42^0tan66^0tan78^0=1.

    Text Solution

    |

  17. If tanalpha=(1-cosbeta)/(sinbeta),t h e n (a)tan3alpha=tan2beta (b) ...

    Text Solution

    |

  18. Prove that: sin36^0=(sqrt(10-2sqrt(5)))/4 .

    Text Solution

    |

  19. The value of (cos3theta)/(2cos2theta-1) is equal to (a) costheta (b) ...

    Text Solution

    |

  20. The value of cos^4theta+sin^4theta-6cos^2theta is (a) cos2theta (b) s...

    Text Solution

    |