Trig: Half-Angle Formulas

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A few problems involving half-angle formulas in trigonometry.

• Category

  Education

[gvilleguy32605]

Wow, if I left the answer at 2/root (5), I would have had partial credit. My teacher went through a lot of trouble rationalizing radicals. Never leave radicals in the denominator. He wanted everything simplified, I guess I am stuck that way myself.

[MathTV]

It is important that trigonometry students know how to rationalize the denominator. But I don't have them do it all the time. It was more important when there were no calculators because getting a decimal approximation to an answer, by hand, is much easier if the denominator is a whole number.

[wtf01s4]

theres 2 kinds of math:

1. memorizing: this is the kind of math that most people think about, and it is a highly perishable skill. usually this kind of math is performed by people who only want to know enough math to pass a test. learning math like this is usually not useful for anything that isn't an exam.

2. understanding: people who solve math problems so that they can understand them usually don't have to rely on memorizing formulas, since they can probably derive whatever they need.

[omgitslisaa]

wow.. i feel like i just learned.. two weeks worth of math that my really bad teacher tried to teach us..

you are amazing!

[poople1000]

textbooks are pieces of shit when it comes to learning, this guy made it make more sense

[metalmatt1017]

Man... I wish this guy was my trig instructor. That is the first time in weeks I've heard these formulas explained in a manner that makes sense.

[XagonogaX]

I have an amazing precalc teacher! I just need more practice is all.

[Adv7d]

Thanks : )

[Yūji Sakamoto]

thx 

[FalzerMaster]

why is he multiplying radical 8/5 by 1/2 in the first example?

[XxkamuixX]

My professor started teaching this, Though i'm still having difficulty with this... I guess I get confused as to where anything goes in terms of Sin, And Cos,etc. I think maybe i'm just confusing myself by trying to mix it with Algebra. Wouldn't it be almost similar to algebra though? Thanks

[mike long]

good video

[Julia Mella]

You make it look easy. Thank youuu. <3