Question 194699
 i m not sure which formula i used can u solve this for me and tell me the formula please.
using formulas evalute 
a. sin 11π/12
b. tan [-5π/12] 
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These are just trig functions in radians.
You can convert the angles to degrees by multiplying by 180/pi.
a. sin 11π/12
= sin(165º)
= ~ 0.9977973
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b. tan [-5π/12]
= tan(-75º)
= ~ 0.4207
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Is that what you need?  If that's not sufficient, email me via the thank you note.