Home
Class 11
MATHS
If A + B + C = 180^(@), prove that co...

If A + B + C = `180^(@)`, prove that
cos A + cos B - cos C = -1 + 4 cos `(A)/(2) cos"" (B)/(2) sin"" (C )/(2)`

Text Solution

Verified by Experts

The correct Answer is:
`-1 + 4 cos ""(A)/(2) cos ""(B)/(2) sin ""(C )/(2)`
Promotional Banner

Topper's Solved these Questions

  • TRIGONOMETRY

    SURA PUBLICATION|Exercise EXERCISE 3.8|18 Videos

  • TRIGONOMETRY

    SURA PUBLICATION|Exercise EXERCISE 3.9|16 Videos

  • TRIGONOMETRY

    SURA PUBLICATION|Exercise EXERCISE 3.6|21 Videos

  • SURAS MODEL QUESTION PAPER -2

    SURA PUBLICATION|Exercise section -IV|7 Videos

  • TWO DIMENSIONAL ANALYTICAL GEOMETRY

    SURA PUBLICATION|Exercise ADDITIONAL PROBLEMS - SECTION - D|3 Videos

Similar Questions

Explore conceptually related problems

If A + B + C = 180^(@) , prove that sin A + sin B + sin C = 4 cos (A)/(2) cos"" (B)/(2) cos"" (C )/(2)

If A + B + C = (pi)/(2) , prove that cos 2A + cos 2B + cos 2C = 1 + 4 sin A sin B cos C

If A+B+C=180^0 , prove that : cos^2, A/2 + cos^2, B/2 - cos^2, C/2 = 2cos, A/2 cos, B/2 sin, C/2

Prove that a cos A + b cos B + c cos C = 4 R sin A sin B sin C.

If Delta ABC is right triangle and if angleA = (pi)/(2) , then prove that cos B - cos C = -1 + 2 sqrt(2) cos"" (B)/(2) sin"" (C )/(2) .

If A + B + C = 180^(@) , prove that sin^(2)A + sin^(2)B + sin^(2) C = 2 + 2 cos A cos B cos C

If A + B + C = 180^(@) , prove that sin^(2)A + sin^(2)B - sin^(2)C = 2 sin A sin B cos C

Prove that cos (A + B) cos (A - B) = cos^(2) B - sin^(2) A

If A+B+C+D = 2pi , prove that : cosA +cosB+cosC+cosD=4 cos, (A+B)/2 cos, (B+C)/(2) cos, (C+A)/2

If A + B + C = (pi)/(2) , prove that sin 2A + sin 2B + sin 2C = 4 cos A cos B cos C