Question

True ??

Answer 1

@Vocaloid

Answer 2

cos(a+b) = ?

Answer 3

cos(a+b)=cosacosb +sinasinb

cos(x/7 + x/7) = cos(x/7)cos(x/7) +sin(x/7)sin(x/7)

Answer 4

on the right side will be

1/2[1- (cos(x/7)cos(x/7) +sin(x/7)sin(x/7))]

Answer 5

or cos 2x = 2cos^2 x -1 so

cos(2x/7)= 2cos^2 x/7 -1

cos^2 x/7 = 1 - sin^2 x/7 = 1 - sin x/7 *sin x/7 so cos(2x/7)= 2(1-sin^2 x/7) -1 =

= 2 - 2sinx/7*sinx/7 -1 = 1 - 2sinx/7*sinx/7

on the right side there are

1/2 [ 1 - cos (2x/7) ] =

1/2 [ 1 - (1-2sinx/7*sinx/7)] =

1/2 [ 2sinx/7*sinx/7) = sinx/7*sinx/7

so this mean that is true sure

hope this will help you understandably

was my pleasure - good luck

Answer 6

@Ultrilliam
@Elsa213

your opinion please - hope is correct solved

Answer 7

@Shadow
@ThisGirlPretty

Answer 8

Sounds good to me :P @Vocaloid

Answer 9

So it is true?

Answer 10

Yes ma'am :P, if it isn't...We will have to kidnap your teacher. >~> (just kidding). @Shadow What do you think? >.<

Answer 11

@SmokeyBrown

Answer 12

I think this is right, yes