Cos (x) = -1/7
Find cos (1/2 x)
Please help me :(
Oh and this is in quadrant II
2007-04-17 12:27:49 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
well in radians it is 1.714143896 for x
so that would be .6546536707
in degrees it would be 98.2132107 for x
making final be the same as above, .6546536707
2007-04-17 12:44:34 · answer #1 · answered by Gelu6713 2 · 0⤊ 0⤋
The half-angle formula tells us that
cos(1/2 x) = sqrt( 1/2 (1 + cos(x)) )
So
cos(1/2 x) = sqrt ( 1/2 ( 1 - 1/7 ) )
cos(1/2 x) = sqrt ( 1/2 * 6/7 )
cos(1/2 x) = sqrt (3/7) = .6547
BTW: Helmut's answer isn't correct (wrong sign) because he's basing off of an angle in Quadrant III, not Quadrant II like is stated in the problem.
2007-04-17 19:49:26 · answer #2 · answered by E Grill 2 · 0⤊ 0⤋
Cos (x) = -1/7
x = 261.7868°
x/2 = 130.8934°
cos(x/2) = -0.6546537
2007-04-17 19:44:18 · answer #3 · answered by Helmut 7 · 0⤊ 0⤋
srry, im not that smart yet:(
2007-04-17 19:38:30 · answer #4 · answered by carr 3 · 0⤊ 0⤋