Hi there!

We are given:
cos(7x)cos(4x) = -1 - sin(7x)sin(4x)
Begin by moving all terms with variables to one side:
cos(7x)cos(4x) + sin(7x)sin(4x) = -1
The corresponding trig identity is cos(A - B). Thus:
cos(7x - 4x) = cos(7x)cos(4x) + sin(7x)sin(4x) = -1
cos(3x) = -1
cos = -1 at π, so:
3x = π
x = π/3
We can also find another solution. Let 3π = -1:
3x = 3π
x = π
Thus, solutions on [0, 2π) are π/3 and π.
Answer:
A
Step-by-step explanation:
given the sequence above using using two as a first term the only formula fits the sequence above is A
Multiply both sides by -4/7
Answer:
90 : 1
Step-by-step explanation:
1 yard = 36 inches
5 yards = 36×5 = 180 inches
180 : 2
90 : 1