It is known that the angle OC is the bisector of the angle AOB and the angle od is the bisector of the angle AOC A. Angle cod = one third angle AOB B. Angle AOD = quarter angle AOB C. Angle AOD = half angle BOC D. Angle cod = one third of angle DOB

A
Angle cod = quarter angle AOB

As shown in the figure, OC is the bisector of ∠ AOB, OD bisectors ∠ AOC, and ∠ cod = 30 °, then ∠ AOB=

∵ od bisection ∠ AOC
∴∠AOC＝2∠COD＝60°
∵ OC bisection ∠ AOB
∴∠AOB＝2∠AOC＝120°

It is known that the ray OC is divided into ∠ AOB, the ray od is divided into ∠ AOC and ∠ 110 degree
1. Find ∠ cod
2. No ∠ COE = 30 °, find ∠ AOD
It should be: known ray OC bisection ∠ BOE, ray od bisection ∠ AOE, and ∠ AOB = 110 degree

Angle AOD = angle doe, angle EOC = angle cob,
Angle AOD + angle DOE + angle EOC + angle cob = 110 degrees,
So, DOE + EOC = 110 degrees / 2 = 55 degrees
That is: cod = 55 degrees
2. If COE = 30 degrees, then angle AOD = (angle AOB angle COE * 2) / 2 = 25 degrees

In order to prevent the spread of influenza A (H1N1), two research institutes a and B have carried out research on it. If they independently study influenza A (H1N1) vaccine, the probability of success of research institute a and B is 1 / 3 and 1 / 4 respectively. It is known that if one research Institute is successful, the economic benefit of this research institute will be 10000 yuan. If two research institutes are successful, the economic benefit will be 10000 yuan, The economic benefit of each research institute is 2 A / 30 thousand yuan. (1) how many ten thousand yuan of economic benefit is expected to be obtained by research institute a's influenza A (H1N1) vaccine. (2) if resources are shared, the benefit will be improved, That is to say, the probability of success of their cooperative research is 20% higher than that of success of at least one independent research?

1. A is successful, B is unsuccessful, probability = 1 / 3 * (3 / 4) = 1 / 4, amount of money obtained = a, a and B are successful, probability = 1 / 3 * 1 / 4 = 1 / 12, amount of money obtained = 2A / 3, so expectation = 1 / 4 * a + 1 / 12 * 2A / 3 = 11a / 36 (ten thousand yuan) 2

Ask a math problem,
The prophet's move deals 275 damage points to the first unit, increasing by 7% each time. How much damage does it take to the 18th unit?

275 (1 + 7%) ^ 17 ≈ 869 damage

Monthly output and sales of a certain brand Juicer: the fixed cost is 28000 yuan per month, the production cost of each production is 60 yuan (the total cost is the sum of fixed cost and production cost), and the functional relationship between sales revenue s (yuan) and output x (unit) is s = - 0.4x + 380x. Assuming that the juicer is sold completely, the profit should not be less than 20000 yuan, What range should the monthly output be controlled in? How many Juicers are produced each month? When the profit is the most, what is the price of each Juicer?

The monthly cost is 28000 + 60 * X
Is the sales revenue s = - 0.4x + 380x? Is this a problem? It should be the square of 0.4x
Profit = s-28000-60x = - 0.4x * x + 320x-28000 = - 0.4 (x * x-800x + 70000) = - 0.4 (X-400) * (X-400)+
twenty-one thousand and six hundred
The first question is - 0.4 (X-400) * (X-400) + 21600 > 20000, that is, (X-400) * (X-400) X-400 > - 100 gets 500 > x > 300
Note that > in the title is greater than or equal to,

As shown in the figure, AB is a 14 arc track with a radius of 0.8m, BC is a horizontal track, the length of BC section is L = 3M, the dynamic friction coefficient of BC section is 115, and an object with a mass of M = 1kg slides down from point a to point C just stops. The work done by the object to overcome the resistance in AB section of the track is calculated. (G is taken as 10m / S2)

Using the motion theorem for the whole process, there is: MGH + W + (- μ MGL) = 0-0, which can be solved by substituting the data: w = - 6J. Therefore, the work of the object overcoming the resistance in AB section of the orbit is 6J. A: the work of the object overcoming the resistance in AB section of the orbit is 6J

All formulas in kinetic energy theorem

G = 0.4 * 10 = 4N f resistance = 0.2 * g = 0.8N
Initial kinetic energy E = 1 / 2m (vsquare) = 20j
No state kinetic energy E = initial kinetic energy - f resistance s = 20-0.8 * 20 = 4J
So there is no state v = (2 radical 5) J

On the positive and negative problems of the formula of kinetic energy theorem
The kinetic energy theorem is that the final kinetic energy subtracts the initial kinetic energy. What if this value is negative? Do you want to add a sign according to the positive and negative work?
Why is the final kinetic energy minus the initial kinetic energy the increment? Isn't it possible to reduce it

Kinetic energy is a kind of energy, which is the same as heat. It is a non vector. It can only be increased or decreased. What do you say about "kinetic energy theorem is that the final kinetic energy subtracts the initial kinetic energy, so what if this value is negative?". If it is negative, it means how much kinetic energy has been reduced

Physics problems of kinetic energy theorem
I hope to analyze each option,

The work done by the supporting force of the floor to the object is equal to the change of the mechanical energy of the object, which is MGH + (1 / 2) MV ^ 2

It is known that the angle OC is the bisector of the angle AOB and the angle od is the bisector of the angle AOC A. Angle cod = one third angle AOB B. Angle AOD = quarter angle AOB C. Angle AOD = half angle BOC D. Angle cod = one third of angle DOB