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    Given that sin(pi/3)=root3/2, and cos(pi/3)=1/2, use trig identities to determine the exact values of sin(2pi/3), cos(2pi/3), sin(5pi/6), and cos(5pi/6). WITHOUT USE OF CALCULATOR.

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    (Original post by Mulkeen)
    Given that sin(pi/3)=root3/2, and cos(pi/3)=1/2, use trig identities to determine the exact values of sin(2pi/3), cos(2pi/3), sin(5pi/6), and cos(5pi/6). WITHOUT USE OF CALCULATOR.

    Thank you x
    This looks remarkably similar to a thread someone posted in the (University) Mathematics forum a couple of days ago

    What have you tried so far?

    What formulas do you know that might help you?
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    To get started. You need to express the target angle in terms of the angles you have using the double angle formula and the formula for sum/difference of angles
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    Use your double angle identities, and as you move on to cos(5pi/6) and sin(5pi/6), you see that they logically follow.
    Hint: cos(2pi/3 + pi/6)...
 
 
 
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