## anonymous 3 years ago give the exact value of f(pi/3) if f(X)=6cosx-10sin2x

1. anonymous

why 7x+4?

2. AravindG

substitute $$x$$ with $$\dfrac{\pi}{3}$$

3. anonymous

ok and then from here I am not clear what do

4. anonymous

Do you know what is the cosine and sine of pi/3?

5. anonymous

cosine pi/3=.9998329795 and sine pi/3=.0182760276

6. AravindG

:) Then whats the problem ?

7. anonymous

Do you know what the unit circle is?

8. AravindG

just put those values in the function get the answer be happy :)

9. anonymous

The values are not correct. cosine of pi/3 is .5

10. anonymous

and sine of pi/3= sqrt(3)/2

11. anonymous

ok. I have the answer my teacher put up on the board which is 3-5$\sqrt3$

12. anonymous

Remember that you are finding the values in radians, not degrees.

13. anonymous

but I cannot seem to get this value

14. anonymous

oh! that helps thanks :)

15. anonymous

|dw:1359283703684:dw|

16. anonymous

Just continue from there.

17. anonymous

|dw:1359283831486:dw|

18. anonymous

oh ok I got it! thank you so much!

19. anonymous

Sure.