How do I evaluate?

1 ⤊

cos 255 degrees subtract cos 195 degrees.

2007-04-03 17:43:29 · 3 answers · asked by harry p 1 in Science & Mathematics ➔ Mathematics

3 answers

Here is a hint, use the half angle formula to figure out what cos(15) is (since you know that cos(30)=sqrt(3)/2). Next, use the angle sum formula to compute cos(240+15) and cos(180+15)--then do the subtraction.

2007-04-03 17:49:37 · answer #1 · answered by bruinfan 7 · 1⤊ 0⤋

cos x - cos y = -2 sin( (x-y)/2 ) sin( (x + y)/2 )

cos 255 - cos 195 = -2 sin(30) * sin (225)

=0.70710678118

2007-04-04 00:52:14 · answer #2 · answered by kefkakrist 2 · 0⤊ 0⤋

0.707106781

2007-04-04 02:51:45 · answer #3 · answered by none 2 · 0⤊ 0⤋