The correct order to express cos3x in terms of cosx is; As shown in steps 1 to 9 below.
The steps to simplify the trigonometric identities cos 3x in terms of cos x are as follows;
Step 1; cos x = cos(2x + x)
Step 2; cos(2x) cosx - sin(2x) sinx
Step 3; 1 - 2sin^2x(cosx) -(2sinxcosx)sinx
Step 4; cosx - 2sin²x cosx - 2sin²x cosx
Step 5; cosx - 4sin²x cosx
Step 6; cosx( 1 - 4sin²x)
Step 7; cosx{1 - 4(1 - cos²x)}
Step 8; cosx{-3 + 4cos²x}
Step 9; 4cos³x - 3cosx
Read more about Trigonometric Identities at; https://brainly.com/question/7331447
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