sin 6t + sin 3t = 0

[nathanralph]

For some reason I don't remember my professor explaining this, and I can't figure it out from the book.

Question: Find solutions in [0, 2pi/3)

sin 6t + sin 3t = 0



Find solutions in [0, 2pi/11)

cos 11u + cos 22u = 0


Can anyone point me in the right direction? I don't even know where to start.

 

[stapel]

Use identities to rearrange things into simpler equations.

. . . . .sin(6t) + sin(3t) = 0

. . . . .2sin(3t)cos(3t) + sin(3t) = 0

. . . . .sin(3t)[2cos(3t) + 1] = 0

. . . . .sin(3t) = 0 or 2cos(3t) + 1 = 0

Solve these two equations.

Use something similar for the second exercise.

Eliz.

 

[nathanralph]

Many thanks!

I was just drawing a blank.