Posted by **jenny** on Wednesday, August 24, 2011 at 4:31pm.

Use the exact values of the sin, cos and tan of pi/3 and pi/6, and the symmetry of the graphs of sin, cos and tan, to find the exact values of si -pi/6, cos 5/3pi and tan 4pi/3.

I have found the answers to the first three using the special tables

sin(ƒÎ/6) = cos(ƒÎ/3) = 1/2

cos(ƒÎ/6) = sin(ƒÎ/3) = ã3/2

tan(ƒÎ/3) = ã3

tan(ƒÎ/6) = 1/ã3

I know that the symmetry of sin(-pi/6 is in the third quadrant, so 7pi/6 =

- 0.5

the symmetry of cos 5pi/3 i have taken 2pi - 5pi/3 to give cos pi/3 = 0.5 but i am not too sure where the symmetry comes in

With the tan I do not quite know where to start. Maybe pi + pi/3.

As for plotting the graphs of sin,cos and tan; I do not know where to start here using the pi radians (whereas as usually I am good at plotting graphs. (perhaps it is an age thing :-(

- math -
**bobpursley**, Wednesday, August 24, 2011 at 5:34pm
Your symbols baffle me. Sorry.

- math -
**jenny**, Wednesday, August 24, 2011 at 6:47pm
what symbols

- math -
**MathMate**, Wednesday, August 24, 2011 at 7:06pm
You have been using alt-251 for square-root, which probably works for Microsoft Word, but not for this forum which requires HTML codes.

For π, type in

& p i ;

(without the spaces in-between) and for

square-root, use

& r a d i c ;

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