Prove that cos 3a = cos (2a+a)cos 3a = 4 cos³a – where from the cos a sin a * cos a give cos a? ? cos 3a = cos (2a +a)cos 2a cos a - sin2a sina(2cos²a-1)cosa-(2sina cos a) sina 2cos³a - cos a - 2 sin²a cos a2 cos³a-cos a - 2(1-cos²a)cos a2 cos³a - cos a - 2cos a + 2 cos³acos3a = 4cos³a-3cos a

Not sure what the question is, but I guess it's to prove that

Expand the left side as

and use the double angle identities to write

Recall the Pythagorean identity:

as required.

answer: answer is c!

ok i got to organize the

3/15 and 12/55

3*

aha

3*4 equals 12 but not

a: no

b:

8/24 12/35

no

gautie

it's c

5/18 = 25/90

5*5=25

18*5 = 90

hope that you!

one more happy customer!

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step-by-step explanation: