Question

how to find sin (5 pi/4).??

Answer 1

you want the exact value of it?

Answer 2

exact value is -1/srt2 ......how do we get this value..??

Answer 3

the exact value is sqrt 2 over 2 not -1 over sqrt2

Answer 4

Ok, think of the unit circle for this.

Answer 5

but in this case its in q3 so it will be a negative

Answer 6

where would sin be a negative value? in quadrants 3 and 4

Answer 7

your reference angle is 45 degrees, at \(\frac{\pi}{4}\)

Answer 8

now just count from \(\frac{1\pi}{4}\) all the way around till you get to \(\frac{5\pi}{4}\)

Answer 9

You should know that \(\frac{\pi}{4} = \left(\frac{1}{\sqrt{2}} \ , \ \frac{1}{\sqrt{2}}\right)\)

Answer 10

But that's why I told you at first where sine is negative, which is in either quad 3 or 4. Knowing this we also found \(\frac{5\pi}{4}\), and that radian is in Q3, meaning sine is negative in that quadrant (takes on all the negative y-values)

Answer 11

yeah i got de ans thanks for coming n doing d job jhannybean.:)

Answer 12

Since we know our x and y-values for our reference radian, and knowing they never change, we see that \(\sin\left(\frac{5\pi}{4}\right) = -\frac{1}{\sqrt{2}}\)

Answer 13

Woo! that's good, good luck!