Trigonometry Question

[jessica22]

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Hi, I want 2 know whether I have solved this problem correctly. Thanks guy.

The value of sin (pi/3) equals to the value of?

a) sin (2pi/3)
b) sin (-pi/3)
c) sin (-5/6)
d) sin (5pi/6)
e) sin (-2pi/3)

sin (pi/3) is sin (60 degree)

since sin (2pi/3) because 2pi/3 is 120...its related angle is 180-120= 60... so A is the answer?

 

[americanpierg]

Hi, I want 2 know whether I have solved this problem correctly. Thanks guy.

The value of sin (pi/3) equals to the value of?

a) sin (2pi/3)
b) sin (-pi/3)
c) sin (-5/6)
d) sin (5pi/6)
e) sin (-2pi/3)

sin (pi/3) is sin (60 degree)

since sin (2pi/3) because 2pi/3 is 120...its related angle is 180-120= 60... so A is the answer?

it helps if u have the unit circle thing memmorized, or at least the first quadrant of it, i usually break it up into pi/6 pieces and pi/4 pieces and go from there to derive the rest. at pi/3 (2pi/6) sine is sqrt3 /2, so to have the same sine value itd have to be in quadrant 2, reflected across the y axis, which would be 4pi/6 or 2pi/3

since sin (2pi/3) because 2pi/3 is 120...its related angle is 180-120= 60... so A is the answer?

...i dont really know what you mean by related angle...unless u mean supplementary angles, which does work but its a new one to me cuz ive never really thought about trig in terms of degrees for a long time now, always thought of it in terms of radians

 

[xxxTheDonxxx]

Hi, I want 2 know whether I have solved this problem correctly. Thanks guy.

The value of sin (pi/3) equals to the value of?

a) sin (2pi/3)
b) sin (-pi/3)
c) sin (-5/6)
d) sin (5pi/6)
e) sin (-2pi/3)

sin (pi/3) is sin (60 degree)

since sin (2pi/3) because 2pi/3 is 120...its related angle is 180-120= 60... so A is the answer?

for this i think of sin as the y value and cos as the x value. sin(pi/3) =square root of 3/2, then i look at the answers... i see that the y value for A is also square root of 3/2 (with positive value like the first one) so that would be the answer.

 

[jessica22]

it helps if u have the unit circle thing memmorized, or at least the first quadrant of it, i usually break it up into pi/6 pieces and pi/4 pieces and go from there to derive the rest. at pi/3 (2pi/6) sine is sqrt3 /2, so to have the same sine value itd have to be in quadrant 2, reflected across the y axis, which would be 4pi/6 or 2pi/3



...i dont really know what you mean by related angle...unless u mean supplementary angles, which does work but its a new one to me cuz ive never really thought about trig in terms of degrees for a long time now, always thought of it in terms of radians

Yeah, that's how I started it off too.. pi/6 is 30, then i just goes... 2pi/6, 3pi/6,... and for the pi/4, then 2pi/4, 3pi/4..etc.

What I mean by related angle is this...

If u have from 0-90 degree (1st quadrant)...your related angle just be your actual angle... for angle from 90<x<180.(2nd quadrant).. then your related angle will be 180 - x... for 180<x<270 (3rd quadrant) related angle would be x-180..... what do you guys think?

 

[luder98]

One approach to solving this type of questions is to memorize the following:

sin(pi-x) = sin(x)
cos(-x) = cos(x)
sin(pi/2 - x) = cos(x)
tan(pi + x) = tan(x)
cotan(pi+x) = cotan(x)

If you can draw the unit circle and sin,cos, tan, cotan, you can figure this out pretty easily. If you can't, just memorize them. They'll come handy. Good Luck.

 

[colt]

related angle = reference angle.

 

[howui3]

One approach to solving this type of questions is to memorize the following:

sin(pi-x) = sin(x)
cos(-x) = cos(x)
sin(pi/2 - x) = cos(x)
tan(pi + x) = tan(x)
cotan(pi+x) = cotan(x)

If you can draw the unit circle and sin,cos, tan, cotan, you can figure this out pretty easily. If you can't, just memorize them. They'll come handy. Good Luck.

i think you mean sin(pi-x)=cos(x)

 

[americanpierg]

One approach to solving this type of questions is to memorize the following:

sin(pi-x) = sin(x)
cos(-x) = cos(x)
sin(pi/2 - x) = cos(x)
tan(pi + x) = tan(x)
cotan(pi+x) = cotan(x)

If you can draw the unit circle and sin,cos, tan, cotan, you can figure this out pretty easily. If you can't, just memorize them. They'll come handy. Good Luck.

lol thats way to complicated for a question like this

 

[luder98]

i think you mean sin(pi-x)=cos(x)

I think you mean sin(pi/2-x) = cos(x) 😉

 

[americanpierg]

I think you mean sin(pi/2-x) = cos(x) 😉

i think u mean d/dx sin(pi/2-x) = -sin(x)