half angle.
2007-10-14 19:36:29 · 3 answers · asked by candy 3 in Science & Mathematics ➔ Mathematics
not with calculator.
2007-10-14 19:39:52 · update #1
cos(112.5°) = cos(90 + 22.5)
= (cos 90°)(cos 22.5°) - (sin 90°)(sin 22.5°)
= 0(cos 22.5°) - 1(sin 22.5°) = -sin(22.5°)
_________
Use the half angle formula.
-sin(22.5°) = -√[(1 - cos(45°))/2] = -√[(1 - √2/2)/2]
= -√[(2 - √2)/4] = -√(2 - √2) / 2
________
cos(112.5°) = -sin(22.5°) = -√(2 - √2) / 2
2007-10-14 20:03:05 · answer #1 · answered by Northstar 7 · 1⤊ 0⤋
cos 112.5° (I assume you mean 112.5°.)
= cos (90° + 22.5°)
= - sin (22.5°)
= - (1/2) [2sin^2(22.5°)]
= - (1/2) (1 - cos 45°)
= - (1/2) (1 - 1/â2)
= - (1/4)(2 - â2).
2007-10-14 19:58:36 · answer #2 · answered by Madhukar 7 · 0⤊ 1⤋
UMMMMM I'm taking a rough guess to 9 decimal places that its 0.382683432 ???????? im no mathematician but that is the answer.... i think????
2007-10-14 19:44:20 · answer #3 · answered by crazy_foz51 2 · 0⤊ 2⤋