Home
Class 12
MATHS
Cosine formula: With usual notations i...

Cosine formula:
With usual notations in any triangle ABC
Prove that : ` cos A= (b^(2)+c^(2)-a^(2))/(2bc) `.

Promotional Banner

Topper's Solved these Questions

  • APPLICATIONS OF VECTOR ALGEBRA

    PREMIERS PUBLISHERS|Exercise SOLUTION TO EXERCISE 6.1|14 Videos

  • APPLICATIONS OF VECTOR ALGEBRA

    PREMIERS PUBLISHERS|Exercise SOLUTION TO EXERCISE 6.2|10 Videos

  • APPLICATIONS OF MATRICES AND DETERMINANTS

    PREMIERS PUBLISHERS|Exercise PROBLEMS FOR PRACTICE (II. Answer the following)|15 Videos

  • COMPLEX NUMBERS

    PREMIERS PUBLISHERS|Exercise Problem for practice|45 Videos

Similar Questions

Explore conceptually related problems

Sine formula: With usual notation in a Delta ABC Prove that (a)/(sin A)= (b)/(sinB)= (c)/(sin C)

In any Delta ABC, prove that the area Delta = (b^(2) + c^(2) - a^(2))/(4 cot A )

In any triangle ABC, prove that a cos A+b cos B +c cos C =(8 triangle^(2))/(abc) .

With usual notations, in any triangle ABC, prove the following by vector method . (i) a^(2)=b^(2)+c^(2)-2bc cos A (ii) b^(2)=c^(2)+a^(2)-2bc cosB (iii) c^(2)=a^(2)+b^(2)-2bc cosC

In a triangle ABC, prove that (b + c)/(a) le cosec.(A)/(2)

In a triangle ABC, prove that b^(2) sin 2C+c^(2) sin 2B=2bc sin A .

In any triangle A B C , prove that: (1+cos(A-B)cos C)/(1+cos(A-C)cos B)=(a^2+b^2)/(a^2+c^2)

In acute angled triangle ABC prove that tan ^(2)A+tan^(2)B+tan^(2)Cge9 .

In any triangle prove that a^2 =(b+c)^2 sin^2 (A/2) +(b-c)^2 cos^2 (A/2)

PREMIERS PUBLISHERS-APPLICATIONS OF VECTOR ALGEBRA-PROBLEMS FOR PRACTICE (Answer the following questions)
  1. Cosine formula: With usual notations in any triangle ABC Prove tha...

    Text Solution

    |

  2. Prove that the sum of the squares of the squares of tha diagonals of a...

    Text Solution

    |

  3. Show that (veca xx vecb) *(vecc xx vecd) +(vecb xx vecc) *(veca xx vec...

    Text Solution

    |

  4. Find the vector and cartesian equation of the line through the point (...

    Text Solution

    |

  5. Find the vector and cartesian equation of the line joining the points ...

    Text Solution

    |

  6. Find the angle between the lines (x-1)/(2)=(y+1)/(3)=(z-4)/(6) and vec...

    Text Solution

    |

  7. Find the distance between the parallel lines vecr=(hati-hatj)+t(2hati-...

    Text Solution

    |

  8. Show that the lines vecr=(hati-hatj)+t(2hati+hatk) and vecr=(2hati-hat...

    Text Solution

    |

  9. Find the vector and cartesian equation of a plane which is at a distan...

    Text Solution

    |

  10. Find the vector and cartesian equation of the plane passing through (2...

    Text Solution

    |

  11. Find the vector and cartesian equation of the plane passing through (2...

    Text Solution

    |

  12. Find the Vector and Cartesian equation of the plane containing the lin...

    Text Solution

    |

  13. Find the vector cartesian equation of the plane passing through the po...

    Text Solution

    |

  14. Find the vector and certesian equation of the plane through the points...

    Text Solution

    |

  15. Find the equation of the plane passing through the points (3, 4, 2), (...

    Text Solution

    |

  16. Find the equation of the plane passingthrough the intersection of the...

    Text Solution

    |

  17. Find the distance between the parallel planes vecr*(-hati-hatj+hatk)=3...

    Text Solution

    |

  18. Find the coordinates of the point where the line vecr=(hati+2hatj-5ha...

    Text Solution

    |

  19. The value of [hati+hatj,hatj+hatk,hatk+hati] is equal to :

    Text Solution

    |

  20. If abs(veca+vecb)=abs(veca-vecb) prove that veca and vecb are perpendi...

    Text Solution

    |

  21. Find the shortest distance between the lines (x-3)/(3)=(y-8)/(-1)=(z-3...

    Text Solution

    |