- #1
Byrgg
- 335
- 0
It's set up like this and you have to solve for all possible angles:
-360 degrees <= theta <= 360 degrees
8cos ^ 2 theta + 7cos theta - 1 = 0
(my work)
(8cos - 1)(cos theta + 1) = 0
8cos theta - 1 = 0
8cos theta = 1
cos theta = 1/8
theta = 1/8 cos ^ -1
theta = 83 degrees
= -83 degrees
= 277 degrees
= -277 degrees
OR
cos theta + 1 = 0
cos theta = -1
theta = -1cos ^ -1
theta = 180 degrees
= -180 degrees
The back of the textbook has only the answers before my "OR", they do not show the possible 180 and -180 degrees that I calculated, did they just forget or did I mess something up?
-360 degrees <= theta <= 360 degrees
8cos ^ 2 theta + 7cos theta - 1 = 0
(my work)
(8cos - 1)(cos theta + 1) = 0
8cos theta - 1 = 0
8cos theta = 1
cos theta = 1/8
theta = 1/8 cos ^ -1
theta = 83 degrees
= -83 degrees
= 277 degrees
= -277 degrees
OR
cos theta + 1 = 0
cos theta = -1
theta = -1cos ^ -1
theta = 180 degrees
= -180 degrees
The back of the textbook has only the answers before my "OR", they do not show the possible 180 and -180 degrees that I calculated, did they just forget or did I mess something up?