I'm not sure if I am doing these problems right. And for some of them I can`t figure out how they would be factored. I'll e-mail what I have done so far. Solve each problem for theta(there is no sign on my computer)for 0 is less than or equal to theta which is less less than 360 2cosx-1=0 cosx=1/2 Anwser 60,300 tanx-2sinxtanx=0 tanx(-2sin+1)=0 (factor ?) tanx=0 and sin= 1/2 (solve from there?) 2sinx-cscx=0 2sinx-1/sinx=0 3sinx-1=0 3sinx=1/3(?) 4cos(2x)+2cosx= -1 8cosx+2cosx+1=0 10cosx+1=0 10cosx= -1/10 (?) cos(2x-30)=1/2 cos2x-cos30=1/2 cos2x-cos30-1/2=0 i don`t know what to do know Sinx+cosx=0 Square both sides? Hi Grant, Here a few hints. 2cosx-1=0 cosx=1/2 Anwser 60,300 tanx-2sinxtanx=0 tanx(-2sin+1)=0 (factor ?) tanx=0 and sin= 1/2 (solve from there?) 2sinx-cscx=0 2sinx-1/sinx=0 3sinx-1=0 3sinx=1/3(?) Here you have a mistake, you should get 2sin2(x) - 1 = 0 4cos(2x)+2cosx= -1 8cosx+2cosx+1=0 10cosx+1=0 10cosx= -1/10 (?) rather than cos(2x) = 2cos(x) (which is false in general), you should use the identity cos(2x) = cos2(x) - sin2(x) = cos2(x) - (1 - cos2(x)) = 2cos2(x) - 1 cos(2x-30)=1/2 cos2x-cos30=1/2 cos2x-cos30-1/2=0 i don`t know what to do know In 1) you solved cosy=1/2 Anwser y = 60,300. Therefore for cos(2x-30)=1/2 you get the answer 2x+30 = 60, 300. Sinx+cosx=0 Square both sides? Claude Go to Math Central