Expert: Sherman D. - 12/17/2004

Question
Find all values of theta in the interval 0<=theta<2pi that satisfy the equation, sin(2theta) +cos(theta)=0

Answer
sin(2 theta) + cos(theta) = 0

sin(2A) + cos(A) = 0

0 <= A <= 2pi
or
0º <= A <= 360º

I went to www.calculator.com, clicked Graphing, and i typed in sin(2x) + cos(x), then clicked enter and it showed me the values

90º and 270º

Each notch is 90ºx

I got those, but there are 2 more x-intercepts, but i can't seem to figure those one out.

Quickmath gives me Pi/2, -Pi/2, and -Pi/6

I believe the -Pi/2 which equals -90, is really 270, it just has -90 instead of 270 because its on the bottom of a degree chart, like at http://math.rice.edu/~pcmi/sphere/drg_txt.html