-2 cos 5A . cos 7A tolong di jawab secepatnya

jawab

- 2 cos 7a cos 5a =
=  - 2 [ cos 12 a + cos 2a ]

-2*(5*cos(A)*sin(A)^4-10*cos(A)^3*sin(A)^2+cos(A)^5)*((-7*cos(A)*sin(A)^6)+35*cos(A)^3*sin(A)^4-21*cos(A)^5*sin(A)^2+cos(A)^7)
disederhanakan
70*cos(A)^2*sin(A)^10-490*cos(A)^4*sin(A)^8+924*cos(A)^6*sin(A)^6-500*cos(A)^8*sin(A)^4+62*cos(A)^10*sin(A)^2-2*cos(A)^12
difaktorkan
2*cos(A)^2*(5*sin(A)^4-10*cos(A)^2*sin(A)^2+cos(A)^4)*(7*sin(A)^6-35*cos(A)^2*sin(A)^4+21*cos(A)^4*sin(A)^2-cos(A)^6)