- #1
salman213
- 302
- 1
1.x = rcos(a)cos(a)
x is known
r is known
I can't seem to get this!
x = -2
r = 7
therefore
-2/7 = cos(a)*cos(a)
so..
-2/7 = cos^2(a)
i know cos^2(a) = 1 + cos2a / 2
-2/7 = 1 + cos2a / 2
so
-4/7 -1 = cos2a
I cannot take cos inverse of this value since it is "greater" than 1 (-1.57)
the book says the angle is 106.6 degrees!
HELP!
x is known
r is known
I can't seem to get this!
x = -2
r = 7
therefore
-2/7 = cos(a)*cos(a)
so..
-2/7 = cos^2(a)
i know cos^2(a) = 1 + cos2a / 2
-2/7 = 1 + cos2a / 2
so
-4/7 -1 = cos2a
I cannot take cos inverse of this value since it is "greater" than 1 (-1.57)
the book says the angle is 106.6 degrees!
HELP!