PreCalculus - Trigonometry: Trig Identities (55 of 57) Solve 2cos(3theta)=1, theta=?

In this video I will solve 2cos(3theta)=1, theta=?

[Muffin--Man]

The correct values are π/9, 5/3*π. The error here was that 360 was not divided by 3. 120-20=100==6/9π-π/9=5/9π.
I make that mistake often too 😣

[NarynbekGilman]

Sir, 100 degrees IS a correct answer because 2cos(3*100 deg) = 2cos(300 deg) = 2cos(360 deg - 60 deg) = 2cos(-60 deg) = 2cos(60 deg) = 2(1/2) = 1.

[dawitdereje]

I think 17/9pi should be thank you so much for explaining

[jiazhang]

What if we want a value between 0 and 360 degrees?

[anishabenny]

Sir, in cos(theta)=1/2, theta can have any value...so can't we write an equation whose solutions are the required angles? Your lectures are great...Thank you....