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Math.sin going out of sync
I am trying to synchronize a pendulum rotated with the tempo of a song.
the tempo is 123 BPM which is 1.025 per second.
I have a slider set to time*1.025 and when I link the rotation of the pendulum directly to the slider (*360) it makes one full revolution exactly on beat for the duration of the song, so I know that 1.025 is the right beats per second.
However when I plug that same number into a typical swing equation:
\\\\\\\\\\\
tempo=(time*1.025)
amp=40;
freq=4;amp*Math.sin(tempo*freq);
\\\\\\\\\\\\\\It becomes un-synchronized. Is there something I am missing about the math behind Math.sin? I feel like it should be making one or two swings per beat depending on the value of “freq”.
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4 Replies
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Try it this way:
freq = 1.025;
swingsPerBeat = 2;
amp=40;
amp*Math.sin(time*freq*swingsPerBeat*Math.PI*2);Dan
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Worked perfectly, thanks again Dan.
Do you mind me asking what about adding “*Math.PI*2” made that difference? I know Math.PI as a javascript function simply represents the number PI (the general ratio of circumference to diameter) but how does that doubled affect this equation? I have seen you use “*Math.PI*2” in other expressions and never really understood what that was achieving.
Thank you it has been quite some time since I took geometry.
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The JavaScript Math functions expect angles expressed in radians, where one complete revolution is equal to 2 times pi.
Dan
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Ohhhh ok, thank you!
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