I was wondering why cos(3pie/4) = cos(-3pie/4)?
I know 3pie/4 is 135 degrees so in 2nd Quad, where only sin is positive.
But how do I know it is equal to cos(-3pie/4)?
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I was wondering why cos(3pie/4) = cos(-3pie/4)?
I know 3pie/4 is 135 degrees so in 2nd Quad, where only sin is positive.
But how do I know it is equal to cos(-3pie/4)?
One way is to use the knowlege that cos is a symmetric function, that isQuote:
Originally Posted by classicstrings
for any real x: cos(x)=cos(-x).
RonL
Ok, is this the same as sin? (tan?) Thanks
sin and tan are anti symmetric, that is for any real x (with the obviousQuote:
Originally Posted by classicstrings
exclusions for tan when it is undefined):
tan(-x)=-tan(x),
and
sin(-x)=-sin(x).
RonL
use this trick: keep in your mind the gognometric circonference; then usinig radians, divide it in the slices you need...you will soon notice that moving clockwise or counterclockwise you'll get to the same point..it's not what you can define a math proof, but it can help you understand...now you should be able to answer to your question about sin and tan