Home
Class 11
MATHS
For a A B C , it is given that cos A+co...

For a ` A B C ,` it is given that `cos A+cos B+cos C=3/2` . Prove that the triangle is equilateral.

Promotional Banner

Topper's Solved these Questions

  • BASIC MATHS,LOGARITHIM, TRIGNOMETRIC RATIO AND IDENTITIES AND TRIGNOMETRIC EQUATION

    ALLEN|Exercise EXERCISE (S-1)|44 Videos

  • Solutions of Triangle & Binomial Theorem

    ALLEN|Exercise Do yourself -6|4 Videos

Similar Questions

Explore conceptually related problems

In a triangle ABC ,cos A + cos B + cos C = 3/2 , then the triangle ,is

112. If in a Delta ABC,cos A+cos B+cos c=(3)/(2). Prove that Delta ABC is an equilateral triangle.

If cos A+cos B+cos C=(3)/(2) in a Delta ABC, then the triangle is

In a triangle A B C , if cos A+2\ cos B+cos C=2. prove that the sides of the triangle are in A.P.

If in a Delta ABC, c(a+b) cos B//2 = b(a+c) cos C//2 , prove that the triangle is isosceles.

In Delta ABC, if cos A+cos B+cos C=(3)/(2) then the triangle is (i) Isosceles (ii) equilateral (iii) Right Angled (iv) none pf these

In a triangle ABC, a cos A+b cos B+ c cos C=

For any triangle ABC,prove that a cos A+b cos B+c cos C=2a sin B sin C

In any Delta ABC, prove that :a cos A+b cos B+c cos C=2a sin B sin C

ALLEN-SOLUTION AND PROPERTIES OF TRIANGLE-All Questions
  1. Value of the expression (b-c)/(r1)+(c-a)/(r2)+(a-b)/(r3) is equal to 1...

    Text Solution

    |

  2. If in a triangle r1=r2+r3+r , prove that the triangle is right angled.

    Text Solution

    |

  3. For a A B C , it is given that cos A+cos B+cos C=3/2 . Prove that the...

    Text Solution

    |

  4. In a triangle A B C , if cos A+2\ cos B+cos C=2. prove that the sides ...

    Text Solution

    |

  5. In a triangle ABC, if angle A=5 5^(@) and angle B=15^@, then c^2-a^2 ...

    Text Solution

    |

  6. The sides of a triangle A B C are x , y ,\ sqrt(x^2+y^2+x y) respectiv...

    Text Solution

    |

  7. If p1,\ p2,\ p3 are the altitudes of a triangle from its vertices A ,\...

    Text Solution

    |

  8. If in a triangle A B C angle B=90^0 then tan^2(A/2) is (b-c)/a (b) (b-...

    Text Solution

    |

  9. If a/(sinA)=K , then the area of "DeltaA B C" in terms of K and sines ...

    Text Solution

    |

  10. In a "DeltaA B C","\ "/"C"=60"\ "&\ /A=75. If D is a point on A C such...

    Text Solution

    |

  11. In a DeltaABC, a semicircle is inscribed, whose diameter lies on the s...

    Text Solution

    |

  12. In a triangle A B C , right angled at B , the inradius is (A B+B C-A C...

    Text Solution

    |

  13. In an equilateral triangle, inradius r , circumradius R and ex-radius ...

    Text Solution

    |

  14. In a triangle A B C ,(r1+r2)/(1+cosC) is equal to (2a b)/(c"Delta") (b...

    Text Solution

    |

  15. With usual notations in a triangle A B C , if r1=2r2=2r3 then 4a=3b (b...

    Text Solution

    |

  16. a, b, x are in A.P., a,b,y are in G.P. and a, b, z are in H.P. then:

    Text Solution

    |

  17. In A B C , if r\ : r1: R=2\ : 12\ :5, where all symbols have their us...

    Text Solution

    |

  18. If a , b ,\ A are given in a triangle and c1a n d\ c2 are two possible...

    Text Solution

    |

  19. If cos A+cos B+2cos C=2 then the sides of the A B C are in A.P. (b) G...

    Text Solution

    |

  20. In a triangle A B C ,\ C D is the bisector of the angle Cdot If cosC/2...

    Text Solution

    |