SOLUTION: What are exact values of sin 7pi/6, tan2pi/3, sec7pi/4, sin(-19pi/6), tan 5pi/6

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Question 29986: What are exact values of sin 7pi/6, tan2pi/3, sec7pi/4, sin(-19pi/6), tan 5pi/6
Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
Either switch your calculator to radians and type in (7*pi)/6 and then find te sin of that. Etc

or convert the radians to degrees first and then find te sin etc.

I shall do the second method, since the first is just you using a calculator.

ALWAYS START WITH WHAT YOU KNOW: 2%2Api radians is 360 degrees

So, pi+=+180

Hence %287%2Api%29%2F6+=+%287%2F6%29%2A180
which is 210 degrees

So sin210 is? use your calculator here. Or, if you truly understand TRIG manipulation, do it by yourself: realise that 210 degrees is in the 3rd quadrant, where sin is always -ve. The equivalent 1st quadrant angle here would be 180+x = 210 --> x is 30. So sin30 is 1/2.

Answer is -(1/2)...check on your calculator that this is correct :-)

You do the rest :-)

jon.