Question

what are the different ways to rewrite 2cosx

Answer 1

Do you mean cos(2x) ? There are 3 different ways to write that.

Answer 2

No, 2cosx

Answer 3

I am trying to solve the equation\[tanx +secx =2cosx\]

Answer 4

you see how you can get the left side to be (sin x + 1) / cos x ?

Answer 5

yeah I did that
but did not know where to go from there

Answer 6

Now multiply both sides by cos x and you get sin x + 1 = (cos x)^2

Answer 7

now rewrite (cosx)^2 as 1 - (sinx)^2

Answer 8

oops i messed up ... the right side will be 2(cos x)^2

Answer 9

yeah I was trying to type that

Answer 10

you are able to get those equations written a lot faster than I can

Answer 11

that's why I don't know what to do with the 2 on the outside

Answer 12

You'll get a quadratic equation with only sin's. Get everything on one side and 0 on the other and solve

Answer 13

how on earth do you use the quadratic formula with trig functions?

Answer 14

I got it to \[\sin ^{2}x+sinx-1=0\] but then what?

Answer 15

I get\[2\sin ^{2}x+sinx-1=0\]

Answer 16

how?

Answer 17

oh you are right, I didn't distribute correctly

Answer 18

\[sinx+1=2\cos^{2}x\]\[sinx+1=2(1-\sin ^{2}x)\]
Distribute the 2 over the 1 and - sin^2x. Need i go further

Answer 19

ohh. ok cool

Answer 20

it'll factor into(2sinx-1)(sinx +1)=0

Answer 21

oh perfect. Thanks!
I am new to this site and would love to give you a medal, but I don't know how to do that either

Answer 22

me too. i'm just really bored. I need to figure out a way to get paid to do this LOL!

Answer 23

No kidding! That would be awesome. you can make some good money tutoring, but this would be way easier