Hi all,
sin330cos150 - cos390sin390 = 0
Prove:
What am I to do with this? Do I convert ll to the one function or......mmmm got nothing.
Any help would be appreciated.
Remember that the trig functions are periodic.
$\displaystyle cos(390)=cos(30)=\frac{\sqrt{3}}{2}$
$\displaystyle sin(390)=sin(30)=\frac{1}{2}$
The other two values are:
$\displaystyle sin(330)=-\frac{1}{2}$
$\displaystyle cos(150)=-\frac{\sqrt{3}}{2}$
If you don't see why these are true, look here: Trigonometric functions - Wikipedia, the free encyclopedia
Scroll down and look at the unit circle next to the paragraph "Unit-circle definitions"