Math problem Help solve the second problem, help solve the math problem, there is an answer must be

Solution: Original form. sinθ(5cosθ^4-10cos²θ(1-cos²θ)1-cos²θ)

sinθ(5cosθ^4+10cosθ^4-10cos²θ+cosθ^4-2cos²θ+1)

sinθ(16cosθ^4-12cos²θ+1)

At 36°, sin ≠0, sin5 =sin180°=0

So 16cos 4-12cos +1=0

Let cos 36°=x

then it is 16x -12x + 1 = 0

x=(3±√5)/8=cos²36°

then cos36°= ((3 5) 8), and >cos36°>cos60°=

cos36°=√((3+√5)/8) = (√5+1)/4

2) Connect the center of the circle to the two adjacent points of the regular 5-sided polygon, and connect these two adjacent points, then the central angle corresponding to the chord is 360° 5=72°

Let the chord length = c, then there is c = r +r -2r * rcos72° = 2r (1-cos(2*36°))) = 2r (1-2*cos 36°+1)=4r (1-(3+ 5) 8)=(5- 5)r 2

Then the side length of a regular pentagonal is 5* [5- 5)r 2]=5r [(5- 5)2].

Connect the two points of the diagonal of the regular 5-sided shape, connect these 2 points with the center of the circle, and the corresponding central angle of the triangle formed is 72 2=4*36°

Let the diagonal length = a, then there is.

a²=r²+r²-2r*rcos(4*36°)=2r²(1-cos(2*2*36°))

2r²(1-2cos²(2*36°)+1)

4r²(1-cos²(2*36°))

4r²(1-(2cos²36°-1)²)

4r²(1-(2*((3+√5)/8) -1)²)

4r²((5+√5)/8)=(5+√5)r²/2

a=√((5+√5)/2)r

So the ratio of the length of the diagonal to the length of the side is: a c = ( ( (5 + 5) 2)r) (5r [(5- 5) 2]) = ( 5+1) 10

So sin180 = 5cos36 4sin36-10cos36 2sin36 3 + sin36 5 = 0

The common factor is sin36(5cos36 4-10cos36 2sin36 2+sin36 4)=sin36[(5cos36 2- 5sin36 2) 2-4sin36 2]=sin36( 5cos36 2- 5sin36 2+2sin36 2)( 5cos36 2- 5sin36 2-2sin36 2).

Since sin36 is not equal to 0, the remaining two terms = 0 respectively solve cos36(One unsolved, one correct).

Let the side length of the pentagonal be a, and use the cosine theorem to find the diagonal xi.e. there is x a

When I see it, I want to vomit, so I can do it myself.

Evil, God??? Bill, Bill, Bill, Uh, uh, uh

（1）(x-1)²-1=0

2）x²-7x+12=0

Chu Chu read the number in question 2 wrong, and the first question was not wrong, and he got the value of * in question 1 after bringing it in.

Think about the fact that the student read the number in question 1 incorrectly, and the second question is not wrong, and he gets the value of * in question 2 after bringing it in.

x=14

That's it, you know.

(2)+ gives 4y+2=0, so y=-1 2, substituting x=z-1, so the symmetrical equation x 1=(y+1 2) 0=(z-1) 1, so that the above equation is t, and the parametric equation is obtained.

x=t，y=-1/2，z=t+1。

(1) Let x10, i.e., f(x1)>f(x2), f(x)=x +1 be a subtraction function on (- 0).

2) Let x10, f(x1)-f(x2)=(x1-x2) (xx1x2)<0, i.e. f(x1).< f(x2), f(x)=1-1 x is an increment function on (- 0).

2.(1) Proof: Set x10, x1-x2<0 by the title

So f(x2)-f(x1)<0

So it follows that this function is a subtraction function.

That is, according to the definition, let x1 and x2 be any two values in the defined field, and x1f(x1)-f(x2)=....Finally, let's simplify and compare the size of the simplification result with 0, less than 0, then f(x1).< f(x2), f(x) is an increasing function in the defined domain, and vice versa is a subtracting function.

And that's a good way to prove that you can't just draw a graph of your own functions.

If you buy x pencils for type A, you will buy 20-x pencils for type B. So the solution is x equal to 10

So A and B; Ten pencils of each type.

If B x is bought, then A is (20-x).

Then we get x=10

If you set A to x, you may not have learned negative number arithmetic, so you can try it another way.

I bought x pencils and y pencils for B.

x+y=20

3x+6y=90

3x+3y=60

y=10x=10

10 wallets for each of A and B.

The second question? You don't have to think about it, you can buy ten sticks, just twenty sticks, nine dollars.

1: 402 (1+403%)=402 (100 million)2:1 (

2:22:3 m³

Here's the answer, I've figured it out, take a look for yourself, I hope the results I calculated can satisfy you, thank you! o( oHa! (*Hee-hee.......):

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