Tips for proving trig identities?

[kdelwat]

Hi all,

I'm having a lot of trouble with proving trigonometric identities, particularly using the compound- and double-angle rules. When I look at the solution it seems so obvious, but I can't find the "tricks" by myself. Does anyone have any checklists of sorts or tips for proving this sort of thing?

[jamesh1234]

One tip I can offer is sometimes it can be easier to start from the right hand side and try to prove it to be the same as the left hand side.With trig identities you just have to do as many exercise questions as possible if you find yourself having trouble with them. Some people can 'see' the solution right away but if you are not one of them, just do as many as possible. There are only so many possible variations with trig identity questions that can be asked since you only have a limited number of identities to work with,

[YellowTongue]

I don't really think that there's an "easy" way to get better at it. Just try and do as many questions as possible and you will start to pick up on all of the tricks that you need to use.

Also, try to look at worked solutions for the questions only when absolutely necessary. It's better if you figure out what you need to do yourself rather than have a book tell you. You'll learn better that way 

[abeybaby]

Hello!

I always found that the easiest thing I could do was to convert everything into sin and cos. So if tan featured, I would write sin/cos instead, or is cosec featured, I would write 1/sin instead. That would generally help, and from there I would try and make all the arguments the same for every circular function. So I would use double angle formulae to make sure everything was sin or cos x, instead of sin or cos2x.

Give that a go and see if it makes things easier!