Question

cos 5x ��������� cos 7x = 0
@perl

Answer 1

Θ

Answer 2

cos A - cos B = -2 Sin (A+B)/2. Sin (A-B)/2

Answer 3

cos(5x) - cos(7x) = 0 ?

Answer 4

yes @perl sorry

Answer 5

you can use this formula to simplify:

cos A - cos B = -2 Sin (A+B)/2. Sin (A-B)/2


where A = 5x and B= 7x

Answer 6

cos(5x) = cos(7x)

Answer 7

take inverse cosine of both sides

Answer 8

midhun, how does that substitution make it easier to solve for x ? (exactly)

Answer 9

i dont really know thats why i posted my question

Answer 10

what are the directions, solve for x ? in degrees or radians

Answer 11

Taking inverse I am not sure about it.. so I chose this method...

Answer 12

@perl

can u please check this link? http://openstudy.com/study#/updates/5466d220e4b05b0e1f1daae8

Answer 13

oh i see

Answer 14

then you used zero product property

Answer 15

But I dont know whether this can be done in a simpler way taking inverse as you said

Answer 16

yess

Answer 17

right, we can take invercosine of both sides

Answer 18

can u just do that for me

Answer 19

sure

Answer 20

btw @kimberlyevens... you understood that method?

Answer 21

cos(5x) = cos(7x)
5x = 7x + 2pi*n
5x = -7x + 2pi*n

Answer 22

what would be the next step?