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March 28, 2015

March 28, 2015

Posted by **ALISON** on Thursday, September 15, 2011 at 10:27pm.

[pie/2, pie]

sin s = radical2/ whole number 2

what is s in radians?

how do i figure this out without the use of a calculator. I drew the graph and located it in the second quadrant and i think the triangle is a 45-45-90 but i don't how to find the radians for the sin of s.

- Trig -
**Reiny**, Thursday, September 15, 2011 at 11:42pmstart with this equation:

π radians = 180°

now divide this by simple whole numbers

e.g.

divide by 2 ---> π/2 = 90°

divide by 3 ---> π/3 = 60°

divide by 4 ---> π/4 = 45°

divide by 5 ---> π/5 = 36

divide by 6 ---> π/6 = 30°

divide by 8 ---> π/8 = 22.5°

etc.

copy this chart into a handy place in your notebook.

you know that the sine is positive in the first and 2nd quadrant.

Since s of sin s in in the second quadrant,

s = π - π/4 = 3π/4 , (180-45 = 135°)

check:

sin 3π/4 = .707106781... = √2/2

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