Question

Find the three formulas for cos 2(theta).

Answer 1

i have 4

Answer 2

you do?

Answer 3

but i''l give 3 only
you know any 1?

Answer 4

Cos2 Theta= Cos(Theta +theta).

Answer 5

no.....
you know this one
cos 2x = cos^2x-sin^2x

Answer 6

yes

Answer 7

now use sin^2x+cos^2x=1

Answer 8

so whats cos^2x from there?

Answer 9

1-sin squared theta?

Answer 10

yes, plug that in cos 2x formula

Answer 11

1-sin squared theta- sin squared theta?

Answer 12

1-2sin squared theta?

Answer 13

yes., thats another formula :)

Answer 14

now last

Answer 15

whats cos^2x from there ......from sin^2x +cos^2x=1

Answer 16

cos squared theta=1-sin squared theta?

Answer 17

or ehh 1- sin squared theta=1-sin squared theta

Answer 18

thats done right?

Answer 19

1=1

Answer 20

sin^2 x =1-cos^2x
put this in cos 2x formula

Answer 21

hmm...

Answer 22

cos squared theta+sin squared theta=1 but isn't the formula...

Answer 23

but could you do sin squared theta=1-1-sin squared theta?

Answer 24

2 sin squared theta=1-1

Answer 25

that would equal zero though

Answer 26

i mean sin^2 x =1-cos^2x
in cos^2x-sin^2x

Answer 27

cos^2x - (1-cos^2x) =...?

Answer 28

2 cos squared theta-1?

Answer 29

there you go, 3rd formula

Answer 30

ty, son goku

Answer 31

welcome ^_^