Question

The value of cos 4A - cos 4B is
(cos A - cos B)*(cos A + cos B)*(cos A - sin B)*(cos A + sin B)
2(cos A - cos B)*(cos A + cos B)*(cos A - sin B)*(cos A + sin B)
4(cos A - cos B)*(cos A + cos B)*(cos A - sin B)*(cos A + sin B)
8(cos A - cos B)*(cos A + cos B)*(cos A - sin B)*(cos A + sin B)

Answer 1

$\implies$

Step-by-step explanation:

➩A+B+C= 180

➩cos4A+cos4B+cos4c

➩cos4(A+B+C) =180

➩cos 4A +cos4B -sin 4(2a)

➩cos4-tan4c

➩1+4cos 2a+cos2b+cos2c

Answer 2

Answer:

=8(COSA-COSB)(COSA+COSB)(COSA-SINB)(COSA+SINB)

Step-by-step explanation:

cos4A-cos4B=2cos22A-1-2cos22B+1=2(cos22A-cos22B)

=2((2cos2A-1)2-(2cos2B-1)2)

=2(4cos4A+1-4cos2A-4cos4B-1+4cos2B)

=8((cos4A-cos4B)-(cos2B-cos2A))

=8(cos2A-cos2B)((cos2A+cos2B)-1)

=8(cosA-cosB)(cosA+cosB)(cos2A-sin2B)