Question

Solve 2 cos^2 y - sin y - 1 = 0, for 0 ≤ y ≤360 degrees.

Answer 1

The values don't work.

Answer 2

2(1-sin^2y)-siny-1=0
1-siny-2sin^2y=0
(2siny-1)(siny+1)=0
siny=-1 or 1/2
y=270,30,150

Answer 3

why??

Answer 4

when y=270
then cosy=0, siny=-1
s0 0-(-1)-1=0

Answer 5

change ur calculator mode from radian to degree...or put the eqivalent radians..of my ans.

Answer 6

see i have shown that y=270 is a root...similarly u can do it by urself for 30 and 150

Answer 7

Sorry, I just realized you're right.
Thanks a lot! :)

Answer 8

good to hear that u have got it..