Trigonometry Proofs Involving Half and Double Angles

I work through 5 examples of verifying trigonometric identities that involve half angle and double angle identities.
I was corrected that what I am trying to prove should not be within the body of the proof. This implies it has already been assumed to be true. So proofs should be shown like this example:
cos^2(x)(tan^2(x)+1)=1
Proof:
cos^2(x)(tan^2(x)+1)=cos^2(x)*sec^2(x)
=cos^2(x)(1/cos^2(x))
=1

[ritik_gupta]

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[patchez]

Smashing the chalk was your best exit yet.

[profrobbob]

You are so welcome! Glad you sought out that extra help and landed on my channel...I hope you will keep me at the top of your help list in the future and share my channel with your friends as well!

[profrobbob]

You're welcome very much. Thanks for seeking these videos out and finding and subscribing to my channel:) I appreciate the support of my subscribers!

[graffitimaster]

I wish you could be my teacher! I learned more in this 17 minute video than i did 2 weeks in my Trig class.

[profrobbob]

left side...right it all in terms of sin & cos. You will also need to find common denominators so you can combine the two terms on the left since the right side is only one term. You will also need to apply the double angle identities while you work on the left side.

[profrobbob]

Take 2x+10 as an example. You can rewrite that at 2x+2*5 and then factor out a common factor of 2 and get 2(x+5). Why only one 2 and not two as the original example? When you redistribute the 2 to check your factoring it must be multiplied to each of the two terms in the parenthesis. I hope this helps and thank you very much for watching!!!

[profrobbob]

HAHA! There are slight variations and the BAM or whatever may occur at any time during my class, but I am pretty animated when I teach:D I am glad you like it. Thanks for watching and spreading the word.

[ironman]

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[nkpersian]

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[profrobbob]

I would start with my video about understanding the basic graphs of sine and cosine and/or look at graphing sine and cosine without a calculator. The domain of Sine and Cosine is all real number, so you only have to worry about range. If you know the amplitude and the vertical shift you will be able to figure out the range.

[profrobbob]

Hello ijlal, I'm glad you are finding my videos so helpful...I do have 423 videos separated by playlist on my channel page...you can search most subjects by keywords to find what you need. If that doesn't help, let me know what you are looking for specifically and I will try to guide you through finding it. I am busy making Calc videos this summer which takes up much of my spare time but maybe I can at least direct you to the help you're seeking.

[ItsTrevolocity]

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[ScotMatson]

Another chalk throw and a "do your homework" jingle! These videos keep getting better and better. Just tested today and felt extremely confident with the outcome. Really enjoyed the meaty proof you closed out this tut with, I think my teacher goes a little easy on us sometimes. Wish I had a instructor like you in High School. Thanks again PRB!

[profrobbob]

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[jacobkoman]

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[profrobbob]

And THANK YOU for watching them! I am currently working on adding to my Calc library since I will be teaching AP Calc next year and would like to have more lessons in place before school starts. Good for you, taking that giant step back into school...commitment is that turning point in your life when you seize the moment and convert it into an opportunity to alter your destiny! (not my quote but love the message)

[brendatelles]

Holy crap! Best teacher out there. Im in college taking trig as a pre req and my professor is the worst. I've used these videos to teach myself and have made A's in all my tests:) thank you!

[alexmandel]

Did all that work for an answer of 2?!?!?! *destroys chalk on the board* I just about died laughing, but your videos are helpful, but I feel like the practice problems might be too easy.

[robingrace]

You are a math God. Thank you for these! They are saving me currently. Nothing this semester has made as much sense as your videos do. I think I might just watch these in class instead??