## sara1234 Help please ? one year ago one year ago

1. soty2013

sure

2. satellite73

you are looking for the number between 0 and $$\pi$$ whose cosine is $$\frac{1}{2}$$

3. satellite73

if you still have that cheat sheet, look at the place on the upper half of the unit circle where the second coordinate is $$\frac{1}{2}$$

4. satellite73

5. Aperogalics

π/3 simple

6. Aperogalics

:)

7. satellite73

ok here is the picture |dw:1351127015253:dw|

8. satellite73

in this picture, $$\theta=\arctan(2)$$ an angle whose tangent is 2 since tangent is "opposite over adjacent" i labelled the opposite side 2 and the adjacent side 1

9. satellite73

the hypotenuse we find by pythagoras, it is $$\sqrt{1^2+2^2}=\sqrt{1+4}=\sqrt{5}$$

10. satellite73

and using sine as "opposite over hypotenuse" we see that the sine of the angle is $\frac{2}{\sqrt{5}}$