text: trig identites? i need an answer quick and fast. i learned some trig identities two days ago and couldn't quite recall how to prove it. i'm doing homework and it's bugging me not knowing how it works.  u can just choose one to work on  sin(90-x)=cosx  csc(90-x)=secx see dude u don't need to recall the table i teach u a style to make it easily  note:- tan=sin/cos     note:- cosec=1/sin , sec=1/cos , cot=1/tan         sine                  sin 0  =  0/4  =0                 sin 30 =  1/4  =1/2        sin 45 =  2/4  =1/√2   sin 60 =  3/4  = √3/2   sin 90 =  4/4  =1           cos 0  =  4/4  =1 cos 30 =  3/4  =√3/2 cos 45 =  2/4  =1/√2 cos 60 =  1/4  =1/2 cos 90 =  0/4  =0  tan 0  =  0 tan 30 =  1/√3 tan 45 =  1 tan 60 =  √3 tan 90 =  1 see what i am doing is writing the degrees then below sin i am writing the numbers from 0 to 4 accordingly.then i am dividing each number (i.e. numbers from 0 to 4)by 4.and lastly i am square rooting the number.for example,let's have a look at the sin 60 degree the number i take is 3 then i divide 3 by 4 (actually keeping the sum in that form makes easy to work with.by that form i mean do not convert it into decimals.let it keep in the fractional form 3/4)   then i am rooting the number which results as follows: √(3/4)=√3/√4 i keep √3 in it's form but i root up 4 which results to 2 (√4=2) thus sin 60 degree is √3/2  and cos comes just the opposite of sine  see the chart sin 0 =cos 90 , sin 30=cos 60 ,sin 45=cos 45 , sin 60=cos 30 , sin 90=cos 0.  so if u want to convert sin 30 degree to cos then u have to apply this formula sin(90-30)=cos 60     note=take (90-x)=y because sin(90-x)=cos x is wrong.x is the degree of sin and if x is also used in case of cos it does mean cos x=sin x because x is the value of sin degree for example, here i take x=30 sin(90-30)=cos 30 do this sum tell that this sum means to say : sin(90-30)=cos 60 so sin=30 and cos =60 then u see these are the other formulas of this kind  sin(90-x)=cos y cos(90-x)=sin y cosec(90-x)=sec y sec(90-x)=cosec y cot(90-x)=tan y tan(90-x)=cot y