Are 5^2+10^2-2*5*10 cos50° and 5^2+10^2-2*5*10 cos130° equal to 7.8 and 13.7?

Answer 1

No.

5 ^ 2 + 10 ^ 2 - 2 * 5 * 10 cos 50° =

25 + 100 - 100 * cos 50° =

25 + 100 ( 1 - cos 50 ° ) =

25 + 100 * ( 1 - 0.64278761 ) =

25 + 100 * 0.35721239 =

25 + 35.721239 =

60.721239

5 ^ 2 + 10 ^ 2 - 2 * 5 * 10 cos 130° =

25 + 100 - 100 * cos 130° =

25 + 100 ( 1 - cos 130 ° ) =

25 + 100 * [ 1 - ( -0.64278761 ) ] =

25 + 100 * ( 1 + 0.64278761 ) =

25 + 100 * 1.64278761 =

25 + 164.278761 =

189.278761