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# Another trig question .. watch

1. sin4feta=cos2feta

how do you write the equation in 2feta?

i have no idea how to write sin4feta as 2feta

thankyouuu
2. the fact that someone can get so far in education to be tackling such equations, yet think the character is spelt "feta", pretty much sums up how upset i am with maths education

in answer to your question - do you know the expansion of sin(A+B) ? It's no different, just that in this case A = 2theta, and B also = 2theta

i hate feta cheese.
3. (Original post by get_inspired)
sin4feta=cos2feta

how do you write the equation in 2feta?

i have no idea how to write sin4feta as 2feta

thankyouuu

The word is theta not feta
4. (Original post by zdo0o)
the fact that someone can get so far in education to be tackling such equations, yet think the character is spelt "feta", pretty much sums up how upset i am with maths education

in answer to your question - do you know the expansion of sin(A+B) ? It's no different, just that in this case A = 2theta, and B also = 2theta

i hate feta cheese.
oh yes i can do that expansion thankyou...my mind just had a blank then for a second..

and apologies for the mistake in spelling i know now..
5. (Original post by get_inspired)
oh yes i can do that expansion thankyou...my mind just had a blank then for a second..

and apologies for the mistake in spelling i know now..
no worries

you maths teacher will rant on about learning the "DOUBLE ANGLE FORMULAE OMFG SERIOUS BUSINESS", i.e. making you learn that:

and

but it's kinda uncessary to memorise that specific case just for your exams - because you can always just work it out in a few seconds using the expansions for sin(A+B) and cos(A+B), which are given to you in the formula booklet.

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