1.

In a triangle ABC, `cos 3A+cos 3B+cos3C=1` and `angleA+angleBltangleC`, then find possible measure of `angleC`.

Answer» Correct Answer - `120^(@)`
`cos3A+cos3B+cos 3C=1`
`rARr 2cos(3(A+B))/(2)cos(3(A-B))/(2)=sin^(2)(3C)/(2)`
`rARr -sin(3C)/(2)cos(3(A-B))/(2)=sin^(2)(3C)/(2)`
`rArr sin(3C)/(2)[cos(3(A-B))/(2)-cos(3(A+B))/(2))0`
`rArr 2sin(3A)/(2)sin(3B)/(2)sin(3C)/(2)=0`


Discussion

No Comment Found

Related InterviewSolutions