Solve cos(x) - cos(3x) + cos(5x)=0?

0 ⤊

Solve cos(x) - cos(3x) + cos(5x)=0?

2007-11-17 17:31:20 · 2 answers · asked by Tung P 2 in Science & Mathematics ➔ Mathematics

2 answers

Sum of cosines rule:
cos(a) + cos(b) = 2 cos((a+b)/2) cos((b-a)/2)

So

cos(x) + cos(5x) = 2 cos(3x) cos(2x). Put this into your equation to get

2 cos(3x) cos(2x) + cos(3x) = 0 or, after factoring,
cos(3x) [2cos(2x) + 1] = 0

Take it from there.

2007-11-17 17:47:26 · answer #1 · answered by Ron W 7 · 0⤊ 0⤋

i guess x=π/2

2007-11-17 17:47:00 · answer #2 · answered by Anonymous · 0⤊ 1⤋