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Mathematics 15 Online
OpenStudy (anonymous):

Assuming K is a whole number, evaluate the following

OpenStudy (anonymous):

\[\sin \frac{ \pi }{ 2 } + 2kpi\]

OpenStudy (perl):

what is sin(pi/2) equal to

OpenStudy (anonymous):

3pi/2

OpenStudy (perl):

sin(pi/2) should equal to 1

OpenStudy (anonymous):

because its on (0,1)?

OpenStudy (perl):

sin ( pi/2 + 2*k * pi ) ?

OpenStudy (anonymous):

ill re-type it hold on please

OpenStudy (perl):

yes it equals to 1, since sin ( x + 2pi*k ) = sin x

OpenStudy (anonymous):

\[\sin(\frac{ \pi }{ 2 } + 2kpi)\]

OpenStudy (perl):

you can add a revolution of 2pi radians or multiples of a revolution to sin sin (Θ + 2pi * K ) = sin (Θ)

OpenStudy (perl):

if you refresh your browser that will render properly

OpenStudy (anonymous):

i dont understand

OpenStudy (perl):

This is a trig identity: sin (theta + 2pi*k) = sin(theta) Hence: sin ( pi/2 + 2*k * pi ) = sin(pi/2)

OpenStudy (misty1212):

HI!!

OpenStudy (misty1212):

you got this or not?

OpenStudy (anonymous):

no

OpenStudy (misty1212):

ok lets go slow because it is really not hard at all

OpenStudy (misty1212):

\[\sin(\frac{\pi}{2})=1\] a fact that you might should memorize, but you can see it from the unit circle

OpenStudy (anonymous):

ok

OpenStudy (misty1212):

the other thing you see from the unit circle is if you go around again, in other words if you add \(2\pi\) to any angle, you are right back where you started from

OpenStudy (misty1212):

this is usually described by saying "sine is periodic with period \(2\pi\)" which just means if you add \(2\pi\) to any number the sine remains the same

OpenStudy (misty1212):

|dw:1423023430406:dw|

OpenStudy (misty1212):

that means \[\sin(\frac{\pi}{2})=1=\sin(\frac{\pi}{2}+2\pi)=\sin(\frac{\pi}{2}+4\pi)=...\]

OpenStudy (misty1212):

they are all one because they are all the same place on the unit circle this is more succinctly written as \(\frac{\pi}{2}+2k\pi\)

OpenStudy (anonymous):

ok

OpenStudy (perl):

all these angles : Pi/2, pi/2 + 2pi, pi/2 + 4pi , ... terminate at the same point on the unit circle

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