if sinx=2/3, find the value of cos2x in simplest fractional form?

7 ⤊

2007-11-24 08:17:55 · 4 answers · asked by kayy♥ 3 in Science & Mathematics ➔ Mathematics

cos 2x = 1 - 2 sin ² x
cos 2x = 1 - 8 / 9
cos 2x = 1 / 9

2007-11-28 03:41:57 · answer #1 · answered by Como 7 · 1⤊ 2⤋

cos (2âx) = 1 â 2âsinÂ² (x)

If sin x = 2/3
then sinÂ² x = 4/9

Then
cos (2âx) = 1 â 2âsinÂ² (x) = 1 â 2â(4/9) = 1/9

2007-11-24 16:21:55 · answer #2 · answered by Anonymous · 2⤊ 0⤋

sin x = 2/3
cos 2x = 1 -- 2 sin^2x = 1 -- 2(2/3)^2 = 1 -- 8/9 = 1/9

2007-11-24 16:26:46 · answer #3 · answered by sv 7 · 2⤊ 0⤋

sinx = 2/3
x = arcsin(2/3)

cos(2x) = ?
cos(2 (arcsin(2/3) ) = ?
= 1/9

2007-11-24 16:23:52 · answer #4 · answered by Elfy 2 · 2⤊ 0⤋