can someone tell me the steps in which i would use to simplify this? I know I need to use the sum and difference formula for cosine just not sure past that part
cos(270° + x)

Question

can someone tell me the steps in which i would use to simplify this? I know I need to use the sum and difference formula for cosine just not sure past that part 
cos(270° + x)

phi · Answer

do you know (from your notes) the formula?

anonymous · Answer

yes, cos(270)cos(x)-sin(270)sin(x)

phi · Answer

cos(270) is one of those you are supposed to know.  Or use your calculator
ditto for sin(270)

anonymous · Answer

im supposed to know those?

jdoe0001 · Answer

so... what's $\bf cos(270^o)\quad and\quad sin(270^o)?$

phi · Answer

yes,  0º, 90º, 180º, 270º and 360º  are "special"

anonymous · Answer

o and -1 from the unit circle I know that

phi · Answer

yes, use those in your expression

jdoe0001 · Answer

$\bf {\color{brown}{ cos(270^o)}}cos(x)-{\color{brown}{ sin(270^o)}}sin(x)\implies {\color{brown}{ 0}}cos(x)-{\color{brown}{ (-1)}}sin(x)\implies ?$

anonymous · Answer

yea thats the part I was confused about! Thank you !

jdoe0001 · Answer

yw