PRECALCULUS HELP!!!!!! PLZZ?

thanks for helping in advance. In my precalc class we are learning about composite argument properties and the cofunction properties. I need help in understanding how to do the problems i think i understand the concept of the arguments but i do not know how to use it and when to use each argument. For example one of the questions are sin(x+60) – cos(x+30)= sinx and you are supposed to use the composite argument properties to show that the given equation is an identity.

If you know of any good websites to help me with precalc please share..thanks

sin(x+60) – cos(x+30)
= sinx cos60 + cosx sin60 – cosx cos30 + sinx sin30
= sinx cos60 + cosx sin60 – cosx sin60 + sinx cos60
= 2sinx cos60
= 2sinx (1/2)
= sinx
———
Attn: cos30 = sin60, and sin30 = cos60

This entry was posted on Tuesday, January 19th, 2010 at 4:44 am and is filed under composite properties. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

3 Responses to “PRECALCULUS HELP!!!!!! PLZZ?”

sahsjing on January 19th, 2010 at 10:23 am

sin(x+60) – cos(x+30)
= sinx cos60 + cosx sin60 – cosx cos30 + sinx sin30
= sinx cos60 + cosx sin60 – cosx sin60 + sinx cos60
= 2sinx cos60
= 2sinx (1/2)
= sinx
———
Attn: cos30 = sin60, and sin30 = cos60
References :
bryan on January 19th, 2010 at 10:47 am

THIS IS THE BEST WEBSITE. I don’t think it has precalculus material, but everything from Calculus onwards. This Really helped me with the work. Lots of examples and information. Easy to follow.
References :
http://tutorial.math.lamar.edu/

Used this to help finish my minor in math.
Fazaldin A on January 19th, 2010 at 11:25 am

sin(x+60) – cos(x+30) = sinx
L.H.S. =
= sinx.cos60 + sin60.cosx – cosx.cos30 +sinx.sin30
= sinx/2 + sqrt(3).cosx/2 – cosxsqrt(3)/2 + sinx/2
= sinx = R.H.S.
References :

Composite