Need help with my calculus

Need help with my calculus.
What is the answer and why?

>cosine function and elementary 2nd degree polynomial = calculus

You deserve to fail desu

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The rest of my quiz is calculus and trig, my bad. I can't grasp why there would be multiple solutions though. I'm thinking the answer is B but then both of those answers are in A and I don't know why there are 4 solutions.

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Thanks, I'll post there.

>I can't grasp why there would be multiple solutions though.
Because it's a fucking second degree polynomial, are you all sorts of retarded?

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This. Also cos(x) = a, x may have 2 periodic solutions.

yes, how could there POSSIBLY be 4 solutions

does anyone know the answer?

OP,

Sub in x = cos(theta) into the equation, and solve the equation like a regular polynomial. Once you get your values of x, x1 and x2, just solve:

x1 = cos(theta) and x2 = cos(theta)

for theta.

2cos(theta) * (cos(theta)+1) = 0
2cos(theta) = 0 or cos(theta) + 1 = 0
cos(theta) = 0 or cos(theta) = -1
theta = acos(0) or theta = acos(-1)
theta = pi/2 + 2pi*n or theta = pi*2pi*n

Oh woops, fucked that up.
cos(theta) * (2cos(theta)+1) = 0
cos(theta) = 0 or 2cos(theta) + 1 = 0
cos(theta) = 0 or cos(theta) = -1/2
theta = acos(0) or theta = acos(-1/2)
theta = pi/2 + 2pi*n or theta = 2pi/3 + 2pi*n

No because this board is full of consumerist sheep. No one here has an engineering background except engineering legos up their nose.

>trig
>can't get why there's multiple answers
Wow you're really bad at this.
Remember how the sinus function goes up and down over and over? Say you're looking for sin(angle) = 0
How many answers do you get?

also 3pi*/2

>I'm thinking the answer is B
>without solving it

You realize your graph has 4 zeroes right?

made me chuckle and reply, good job user

Add 1 on both sides and use Newton's formula.
Now back to the homework board.

I cannot grasp the wording "best available".

2*(cos theta)^2 cos theta = 0
=>
cos theta = 0
cos theta = -1/2
=>
theta = Pi/2, 3*Pi/2
theta = 2*Pi/3, 5*Pi/3

2*Pi/3, 5*Pi/3, Pi/2, 3*Pi/2

Every variant contains wrong solution.

Best available probably means most specific while in the bounds given by the question.

I'm not sure why they phrase it like that.

>theta = 2*Pi/3, 5*Pi/3
Disregard that, it's

theta = 2*Pi/3, 4*Pi/3

so 3rd variant does not contain non-solutions.

Disregard that, 1st variant lists all solutions and nothing more.

I'm pretty sure this is a troll exploiting how bad Sup Forums is at math.

So Sup Forums

what is the answer?

E

A