Ratio is the comparison of sizes of two quantities of the same unit. Proportions are the equality of two ratios. A/b =c/d
change,c = 20 - p
so in Excel for example
put 20 in column a
put 11.59, 17.50 etc in column b
in column c put the equation '=20 - b1'
Answer:
x ∈ {2π/3, π, 4π/3} ≈ {2.09440, 3.14159, 4.18879}
Step-by-step explanation:
The equation can be put into standard form by adding 1:
2cos²(x) +3cos(x) +1 = 0
(2cos(x) +1)(cos(x) +1) = 0
Values of cos(x) that make this true* are ...
cos(x) = -1/2 . . . . . . . . . true for x=2π/3, x=4π/3
cos(x) = -1 . . . . . . . . . . . true for x=π
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A graphing calculator can be helpful here, too.
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* from your knowledge of the short table of trig functions and their signs in different quadrants