To determine the centroid, we use the equations:
x⁻ =
1/A (∫ (x dA))
y⁻ = 1/A (∫ (y dA))
First, we evaluate the value of A and dA as follows:
A = ∫dA
A = ∫ydx
A = ∫3x^2 dx
A = 3x^3 / 3 from 0 to 4
A = x^3 from 0 to 4
A = 64
We use the equations for the centroid,
x⁻ = 1/A (∫ (x dA))
x⁻ = 1/64 (∫ (x (3x^2 dx)))
x⁻ = 1/64 (∫ (3x^3 dx)
x⁻ = 1/64 (3 x^4 / 4) from 0 to 4
x⁻ = 1/64 (192) = 3
y⁻ = 1/A (∫ (y dA))
y⁻ = 1/64 (∫ (3x^2 (3x^2 dx)))
y⁻ = 1/64 (∫ (9x^4 dx)
y⁻ = 1/64 (9x^5 / 5) from 0 to 4
y⁻ = 1/64 (9216/5) = 144/5
The centroid of the curve is found at (3, 144/5).
Answer:
150˚ or 330˚
Step-by-step explanation:
It is easier to use the calculator, but you can use the unit circle too.
Calculator:
Plug in the equation without the negative, and you get 30˚ which is your reference angle. But since tangent is negative, the angle is in either the second quadrant, or the fourth (because tangent is negative in these quadrants). Now using your reference angle, you can find the answer.
180 degrees in a triangle therefore you will subtract 54 and 79 from 180 which then gives you the answer --47--
do you understand how to do it now ?
I'm pretty sure it's C. It seemed confusing at first to me, too. Good luck on your test!