Question

help @jim_thompson5910 For what x-value(s) does sin(x) = -1? (Points : 2)
-270°, -90°, 90°, and 270°
-270°, -90°, 0°, 90°, and 270°
-90 and 270°
-270° and 90°

Answer 1

use the unit circle to find out which points on the unit circle have a y coordinate of 1, then record the angle for each point you found

http://www.regentsprep.org/Regents/math/algtrig/ATT5/600px-Unit_circle_angles_svg.jpg

Answer 2

y coordinate of -1 I meant to say

Answer 3

how do you do it?

Answer 4

@jim_thompson5910 i see 270

Answer 5

good, so sin(270) = -1

this is the only angle in the interval from 0 degrees to 360 degrees where sine is -1

Answer 6

all you need to do is list coterminal angles as well and you're done

Answer 7

how do you do that?

Answer 8

if you have any angle x, then a coterminal angle is x+360*n where n is any integer

Answer 9

ex:

if x = 30 and n = 1, then x+360n = 30+360*1 = 30+360 = 390

so the angle 390 degrees is coterminal to 30 degrees

Answer 10

so its 270 and 90

Answer 11

sin(90) = -1 ??

check the unit circle to confirm or deny this

Answer 12

i see 60,45?

Answer 13

locate the 90 degree angle

what's the y coordinate of the point at this angle?

Answer 14

its 1

Answer 15

so sin(90) = 1

and NOT -1

Answer 16

so if sin(x) = -1 then x cannot be 90 degrees

Answer 17

-90,270
because sinx is negative in 3rd & 4th quadrants.
sinx =-1=-sin 90=sin(-90),sin270
hence x is -90 & 270 in the given interval