4 cos² x - 3 = 0
4 cos² x = 3
cos² x = 3/4
cos x = ±(√3)/2
Fixing the squared cosine doesn't discriminate among quadrants. There's one in every quadrant
cos x = ± cos(π/6)
Let's do plus first. In general, cos x = cos a has solutions x = ±a + 2πk integer k
cos x = cos(π/6)
x = ±π/6 + 2πk
Minus next.
cos x = -cos(π/6)
cos x = cos(π - π/6)
cos x = cos(5π/6)
x = ±5π/6 + 2πk
We'll write all our solutions as
x = { -5π/6, -π/6, π/6, 5π/6 } + 2πk integer k
Answer:
9) C. 35 + 0.12x = 44.36
10) B
11) A. 32
Step-by-step explanation:
9)
44.36 is the TOTAL so the equations have to EQUAL it.
PER mile means it's a variable so it's 0.12x:
35 is a constant so there's no variable attached:
35 + 0.12x = 44.36
10)
B because you have to cancel the y values and to do that, you multiply the 1st equation by 3.
11)
0.1x + 0.25(46 - x) = 6.70
0.1x + 11.5 - 0.25x = 6.7
-0.15x = 6.7 - 11.5
-0.15x = -4.8
x = 32
Answer:
z = 106, y = 23
Step-by-step explanation:
z and 74 is a supplementary angle which is equal to 180 degrees.
z + 74 = 180
z = 106
5y - 9 and z is a vertical angle, so the are equal to
each other.
5y - 9 = z
5y - 9 = 106
5y = 115
y = 23
Answer x = 12 and y = 9
Step by step
First identify the equations
The sum of two numbers is 21
x + y = 21
Change to y intercept for ease of math
y = 21 - x ( call this equation a)
Three times the larger is equal to four times the smaller
3x = 4y (call this equation b)
Now substitute the value of y = 21 -x into equation b
3x = 4(21-x)
Distribute
3x = 84 - 4x
Now we want to isolate x by adding 4x to each side
3x + 4x = 84 -4x + 4x
Combine like terms
7x = 84
Now solve for x by dividing both sides by 7
x = 12
Now to find y
Using equation a from above
y = 21 - x
Substitute our x value of 12 into equation
y = 21 - 12
solve for y
y = 9
Now check your work
x = 12 and y = 9
The sum of two numbers is 21
12 + 9 = 21
Three times the larger (x) is equal to four times the smaller (y)
3x12 = 4x9
36 = 36
Problem solved!!
2 x b < 19
< is the less than sign
