Solving polar coordinate equation of straight line

Let the linear equation be ax + by + C = 0
If x = rsin θ, y = RCOs θ
So arsin θ + brcos θ + C = 0

In the triangle ABC, the opposite sides of ∠ a, B and C are a, B and C respectively. If C = 3A and ∠ B = 30 °, then ∠ C=______ ．

∵ C = 3A, ∠ B = 30 ° can be obtained from the cosine theorem, B2 = A2 + c2-2accosb = A2 ∵ B = a, a = 30 ° and C = 120 ° so the answer is: 120 °

1. The radius of the earth is 6400 km_____ CM.
2. The weight of an elephant is about 2.3 tons, equivalent to_ Kg · kg_ Gram
The time of a class is 45 minutes Seconds
4. A student measured that his pulse frequency per minute was 75 seconds. From this, he calculated the time of each pulse_ When he went up the escalator in the shopping mall, he used his pulse as a timing tool. He measured that the number of pulsations from the bottom of the building to the second floor was 60. What was the time that the student took the elevator____ Seconds

1) 640000000
2) 2300 ; 2300000
3) 2700
4) 0.8 ; 48

It is known that x satisfies the inequality 2 (log2x) ^ 2-7log2x + 3 less than or equal to 0
Find the maximum and minimum values of the function f (x) = log2 (x / 2) * log2 (x / 4)

2(log2x)^2-7log2x+3

One side of an isosceles triangle is 6, and an external angle is 120 degrees to calculate the circumference of the triangle

The inner angle corresponding to the outer angle of 120 degrees is 60 degrees
Assuming that the inner angle is the base angle of an isosceles triangle, the triangle is an equilateral triangle with a circumference of 6 × 3 = 18
If the inner angle is the vertex of an isosceles triangle, then the triangle is an equilateral triangle with a circumference of 6 × 3 = 18

The resistance of inductance and capacitance to alternating current is not only related to the inductance and capacitance itself, but also related to the frequency of alternating current
Low flow, why?

Inductance: DC, AC, low frequency, high frequency
Capacitance: AC, DC, high frequency, low frequency

Set u = (1.2.3.4.5.6.7.8.9) Cu (a ∪ b) = (1.3) a ∩ cub = (2.4) then set B?
The answer is {5.6.7.8.9}, but I think since it's a ∩ cub, will there be one that belongs to cub but does not belong to a?

The intersection of a must be contained in a

If we know the line AB, let AB go to C, make BC equal to half AB, and D is the midpoint of AC. if DC equals 6cm, find the length of line ab

∵ D is the midpoint of AC
∴AC=2DC=12cm
∵BC=1/2AB
Let BC be X
We get x + 1 / 2x = 12
The solution is x = 8
That is ab = 8cm
Typing is so tiring,

It is proved that the inverse matrix of an upper triangular matrix with all principal diagonal elements 1 is also an upper triangular matrix with all principal diagonal elements 1

Since there are diagonal elements, the matrix should be n-order square matrix. First, divide the matrix into blocks
A B
C D (1) four blocks, no matter whether n is a multiple of 2 or not, of course it is not better, because if n is not, we can first divide d into 1, that is, the element in the bottom right corner. Here C is obviously a 0 matrix, because the upper triangle. The inverse matrix of the partitioned matrix is
A inverse - a inverse BD inverse
0 d inverse (2) where d inverse is 1, the upper right corner can be ignored, because it has nothing to do with what we want,
Then a is partitioned in the same way, and a (2) similar matrix is also obtained. In this way, the matrix is partitioned continuously until the upper left corner is 1 A
The inverse of (3) is 1-A
0 1（4）,
All the matrices of the right lower corner are 1, and all the matrices of the right upper corner are independent
We obtain an upper triangular matrix whose diagonal elements are all 1

Find the range of y = x & # 178; + 2x (x ∈ [- 2,3])

y=x²+2x=(x²+2x+1)-1=(x+1)²-1
The symmetry axis of the function image x = - 1, with the opening upward
So when x = - 1, we get the minimum value y = - 1
When x = - 2, y = 4-2 × 2 = 0
When x = 3, y = 3 & # 178; + 2 × 3 = 15
So when x = 3, the maximum value y = 15 is obtained
So the range is y ∈ [- 1,15]

Solving polar coordinate equation of straight line