need someone to check my work

A

abel muroi

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Jan 13, 2015
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I was given the problem sin 225 and was told to find the exact value of the trig function

I would show you my work but i can't draw a unit circle here..




I know the reference angle of this trig function is 45 degrees so i drew a 45, 45, 90 triangle..

so my answer is -(squareroot of 2)/2

did i get the correct answer?

((btw i rationalized my answer))
 
Last edited:
abel muroi said:
I was given the problem sin 225 and was told to find the exact value of the trig function

I would show you my work but i can't draw a unit circle here..




I know the reference angle of this trig function is 45 degrees so i drew a 45, 45, 90 triangle..

so my answer is -(squareroot of 2)/2

did i get the correct answer?

((btw i rationalized my answer))
Click to expand...
Yep. good job.
 
abel muroi said:
what about the problem sin 270?

this trig function does not have a reference angle so i cant draw a triangle to find the exact value..

what am i supposed to do?
Click to expand...
Can you draw a triangle for 250? The sin is the opposite over the hypotenuse, so what happens to the length of the opposite side as the angle increases to 260, then 261, then 262, ...?
 
Ishuda said:
Can you draw a triangle for 250? The sin is the opposite over the hypotenuse, so what happens to the length of the opposite side as the angle increases to 260, then 261, then 262, ...?
Click to expand...

why do i have to draw a triangle for 250?

if i draw a triangle for 270, then i have a 90 degree angle, but im not sure what the other two angles are.
 
abel muroi said:
why do i have to draw a triangle for 250?

if i draw a triangle for 270, then i have a 90 degree angle, but im not sure what the other two angles are.
Click to expand...
If the angle is a multiple of 90 (and 270 is!) then you can use the graph of the sine or cosine function (in your case draw the sine graph)
 
abel muroi said:
why do i have to draw a triangle for 250?

if i draw a triangle for 270, then i have a 90 degree angle, but im not sure what the other two angles are.
Click to expand...
you were saying you didn't have a reference triangle. If you drew triangles for 250, then 260, then 265 you should notice that the opposite side is getting closer and closer in length to the hypotenuses and the triangle was getting closer and closer to a straight line. Finally, at 270, the opposite side would be the same as the hypotenuses and on the unit circle the adjacent side would be zero, the opposite side would be -1 and the hypotenuses would be one.
 
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