Question

cosh 3x=4 cosh³x-3 cosh x​

Answer 1

Answer:

idk about cosh it's not in my class i am sorry

Answer 2

Explanation:

cos3x=cos(2x+x)

=cos2xcosx−sin2xsinx

=(−1+2cos

2

x)cosx−2cosxsinxsinx

=−cosx+2cos

3

x−2sin

2

xcosx

=−cosx+2cos

3

x−2(1−cos

2

x)cosx

=−3cosx+4cos 3 x

Hence, cos3x=4cos

3x−3cosx