Sin graphs

[dingo]

Hi,
I am a bit confused with part b. What I thought I was supposed to do was get 45, 135 and 405 degrees and divide them by 3 because 2.5 in this graph would be the same as these three values in a sin graph with a magnitude of 1 and then divide them by 3 because the period is divided by 3. This gave me an answer of pi/12, 3pi/4 and 9pi/4. This wasn't the answer though so would somebody please be able to explain to me what I did wrong The answers were pi/18, 5pi/18 and 13pi/18.

 

[Otis]

… would be the same as [45, 135 and 405 degrees] in a sin graph with a magnitude of 1…

Hi dingo. I'm thinking you'd written

sin(3∙t) = 1/2

and then considered the first three angles where sin(angle)=1/2.

That's good, but the sine of 45º, 135º and 405º is (√2)/2, not 1/2.

?