Good morning all!
There is a problem that I am unable to solve:
Find the exact value of cos[3(pi)/8].
I can't figure out how to solve that for exact solution. My teacher said to use a double-angle identity but I am very confused. My class is new to all this. So any help regarding this problem would be appreciated. Also if it isn't asking to much, can you show the steps if you are able to help me.
Well, my method is not hard to understand, but the first formula can be derived as follows:
Consider the double-angle cosine formula
Substitute after that make the subject of the formula and you're done.
I dunno if the method by applyin' the double-angle cosine formula leads an easy or hard way to compute what you want. (Since I haven't tried.)
Thank you. You made it a bit more clear to me. You are right when you say that your method isn't to hard to understand. I get most of it except the first part. I dont understand the concept of Honestly, I've never seen that before as I don't think my class has learned it so i don't understand the concept of that. That is why I'm asking if there are other methods, but I appreciate your response.
Haha, no problem!
The only reason to use such formula is that
Then plug that into the aforesaid formula. Now, why did I do this? 'cause I knew that evaluating leads an easy computation. (See post #2.)
Since and since we're workin' with a nice angle the expected value will be easy to handle.
The rest are just arithmetic calculations.