# Could really do with a last minute genius to explain trig identities?! Would be grateful of any help :)

Am really struggling with Trig Identities, any help would be greatly appreciated, Thanks :)

Posted Wed 23rd May, 2012 @ 19:11 by Bethan Rogers

## 3 Answers

In Trig Identities Remember Always Sin(thetha)/cos (theta) = Tan(theta)

Cos^2(x)+Sin^2(x)=1 ..... If this is given And you need to show it in a certain form See what they have give you re arrange it to get that and put it into the Question e.g. 2Cos^2(x)+sin(x)=7 and you have to get this into the form of Sin^2 all of it .. This is what you do we know cos^2(x) is same as 1-sin^2(x) So we put this in place of Cos^x and we have 2 (1-sin^x) + sin(x) - 7=0 Expand it and you shud Get 2 -2sin^2(X)+sin(x)-7=0 ... -2sin^2(x)+sin(x)+5=0 Times by -1 to make it positive after That E.g Say Sin(x)=y Factorise it and work out What it is and from there you can work out your angells

Answered Wed 23rd May, 2012 @ 19:20 by maiwand said

Is this for C2??

If so there are just three simple ones

tan(x)=sin(x) over cos (x)

Cos^2(x)=1-sin^2(x)

sin^2(x)=1-cos^2(x)

You are probably going to have to form a quadratic so first change any tans using the first one then change the squared one. At c2 they're it's generally pretty obvious what you have to do, If it isn't, just try differenty ones till you get an equation with all the same function in.

Hope this helps!!

Answered Wed 23rd May, 2012 @ 21:37 by Oliver

SOH CAH TOA (sin, cos, tan) if the opposite and hypoteneuse are left choose SOH/sin (it has OH in it which stands for opposite, hypoteneuse) if the adjasent and the hypoteneuse are left choose CAH/cos ( it has AH in it meaning adjasent, hypoteneuse) and if it is the opposite and the asjasent then it is TOA/tan ( it has the opposite and the adjasent). If you have problems remenbering SOH CAH TOA here is a tip, Sun On Holiday (SOH) Can Affect Health (CAH) Towards Old Age (TOA)

Answered Mon 25th March, 2013 @ 10:05 by MeLoN