The answer is either b or c
cos4x = cos2x
We know that:
cos2x = 1-2cos^2 x
==> cos4x = 1-2cos^2 (2x)
Now substitute:
==> 1-2cos^2 (2x) = cos2x
==> 2cos^2 (2x) + cos2x - 1 = 0
Now factor:
==> (2cos2x -1)(cos2x + 1) = 0
==> 2cos2x -1 = 0 ==> cos2x =1/2 ==> 2x= pi/3
==> x1= pi/6 , 7pi/6
==> x1= pi/6 + 2npi
==> x2= 7pi/6 + 2npi
==> cos2x = -1 ==> 2x= pi ==> x3 = pi/2 + 2npi.
<span>==> x= { pi/6+2npi, 7pi/6+2npi, pi/2+2npi}</span>
Answer:
you cant solve for x but
55x/11x=5x
Step-by-step explanation:
Answer:
C) It is the only solution to the system.
Step-by-step explanation:
3x + 3y = -30
2x + y = -17
3(-7) + 3(-3) = -30
-21 + -9 = -30
-30 = -30
True
2x + y = -17
2(-7) + (-3) = -17
-14 + -3 = -17
-17 = -17
True
