Question

sin2x+cos2x=0
find all solution in 0 is less than or equal to x < 2pi

Answer 1

If it makes it less confusing write it as this:
let u=2x (so u/2 =x)
I'm going to put this strictly in terms of u like so
sin(u)+cos(u)=0 0 <= u/2<2pi (solve for u)
sin(u)=-cos(u) 0< =u<4pi

so you need to find when sin(u) is the opp of -cos(u) for when u is between 0 and 4pi

Answer 2

use unit circle

Answer 3

http://etc.usf.edu/clipart/43200/43215/unit-circle7_43215_lg.gif
here look at the order pairs
when are the ordered pairs opposites
(ex. opp of 3 is -3; -3 and 3 are opps)

Answer 4

i dont get it

Answer 5

I'm asking you to look at the ordered pairs and tell for which angles they are opposite?

Answer 6

the only time you will have they are opposite is when one is sqrt(2)/2 and the other is -sqrt(2)/2