guter Ansatz:
\( -\frac{cos(4x)}{4} - cos(2x) = -2(cos(x))^{4} + c \)
Bedenke (Addtheorem) cos(2x)= 2 cos^2(x) - 1 ==>
\( -\frac{cos(4x)}{4} - ( 2 cos^2(x) - 1 )= -2(cos(x))^{4} + c \)
\( -\frac{cos(4x)}{4} - 2 cos^2(x) + 1 = -2(cos(x))^{4} + c \)
==> \( -cos(4x) - 8 cos^2(x) + 4 = -8(cos(x))^{4} + 4c \)
==> \( cos(4x) = - 8 cos^2(x) + 4 +8(cos(x))^{4} - 4c \)
Und Addtheorem für cos(4x) ist 8cos^4(x)-8cos^2(x)+1 einsetzen
==> \( 8cos^4(x)-8cos^2(x)+1 = - 8 cos^2(x) + 4 +8(cos(x))^{4} - 4c \)
==> 1 = 4 -4c ==> -3 = -4c ==> 3/4 = c