Solve Trigonometric Equation Double Angle Formula

In this video I will show you how to solve a trigonometric equation using the double angle for cosine. When applying the double angle of cosine we are given a quadratic equation where we will now need to factor and solve using the zero product property. We will then determine the solutions on the interval [0,2pi) and all solutions.
I make short, to-the-point online math tutorials. I struggled with math growing up and have been able to use those experiences to help students improve in math through practical applications and tips.
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[@newvisionministriescameroo4058]

I think this man is a living god

[@brysonvansickle9842]

I wish this dude was my teacher this man is a goat

[@DRMath]

Thanks Mr. McLogan for sharing the knowledge!
Happy Teaching ✌️

[@enriquemo2]

Steven Stocker not cool 😡😡😡😡😡😡😡

[@brianmclogan]

You are very welcome Harjeet

[@ibmduh]

For b, it should be + 2pi/3 * n

[@thestovietunion790]

Another (basic) way to solve the question:
-cos(x) = cos(pi+x)
=>cos(2x) = cos(pi+x)
2x = (2n+1)*pi+-x
2x+-x = (2n+1)*pi
Solution Group A: 2x+x = (2n+1)*pi => 3x = (2n+1)*pi => x = (2n+1)*pi/3
Solution Group B: 2x-x = (2n+1)*pi => x = (2n+1)*pi
We can see that group A contains group B in it. There is no need in the equation of group B.
We are left with
x = (2n+1)*pi/3
And those are all the solutions (with n being natural, of course).

[@carlosgarcia1468]

Hi Sir, i think it is pi/3 + 2pi/3 times n. Bec 120 degrees is 2pi/3.

[@jsoho3395]

what grade are you teaching???

[@georgebakradze3202]

If n equals 1 then pi/3+pi/3=2pi/3 and we get negative half. So maybe the solution is right when n is even number.

[@brianmclogan]

👍

[@kawtherbille9398]

Tnx teacher...🥰

[@theimpossiblecastillo8158]

So helpful!!

[@ananyavishwas7455]

You will be live today right?

[@brianmclogan]

No, Sunday