The first n terms and Sn = a1 + A2 + a3 +... Of known sequence an +If an satisfies an + 2snsn-1 = 0 (n is greater than or equal to 2) A1 = 1 / 2, calculate an

The first n terms and Sn = a1 + A2 + a3 +... Of known sequence an +If an satisfies an + 2snsn-1 = 0 (n is greater than or equal to 2) A1 = 1 / 2, calculate an

The second sequence is Sn (1) / Sn (1) + sn-2s (1) + sn-1 (1)
Unit conversion
20ml=（ ）cm²
20ml=（20 ）cm3
Please click "select as satisfactory answer"
Are you making fun of me? Pro, one is the unit of volume, the other is the unit of area, if the following is CM & # 179, then the answer is 20
Write a program to calculate the area of triangle with C language
Suppose that the three sides of a triangle are a, B, C. The procedure is as follows: # include
#include
double area (double a, double b, double c){
double area=0,s=0;
s=(a+b+c)/2
area=sqrt(s*(s-a)*(s-b)*(s-c));
return area;
}
void main(){
double a=10, b=10, c=10;
/*Or use scanf() to enter the value of ABC*/
printf("area=%.2f",area(a,b,c));
}
1. It is known that the sum of the first several terms of the sequence {an} is Sn and satisfies A1 =, an = - 2snsn-1 (n ≥ 2)
1. It is known that the sum of the first several terms of the sequence {an} is Sn, and satisfies A1 = 1 / 2, an = - 2snsn-1 (n ≥ 2)
Whether the sequence {an} is an arithmetic sequence, please prove the above conclusion
Finding Sn and an
If an = - 2Sn (SN an), then 2sn2-2snan + an = 0
The solution is: an = (5-3n) / 4
sn＝（7n-3n2）/8
I don't know how to make olive vinegar,
500 grams of Olives, 150 grams of vinegar, 250 grams of rock sugar
I have 10 jin olives now. How many jin vinegar and rock sugar do I need now?
Note: to specific figures, to Jin as a unit!
500 / 150 = 10 / x, x = 1500 / 1500 = 1 jin vinegar
500 / 250 = 10 / y, y = 2500 / 500 = 5 jin rock sugar
What's the ratio of olive to coarse ingredients? 500 g = 1 kg, 150 g = 0.3 kg, 250 g = 0.5 kg, there should be a ratio, tell me to do it. Take it! Mission
500:150:250=10:3:5
10 olives 3 vinegar 5 rock sugar
500g = 1 kg, vinegar needs 3.3 kg, rock sugar 5 kg
C language program, input the length of the three sides of the triangle, judge whether it is a triangle, if so, judge what kind of triangle, and find its area
#include
#include
//Minimum accuracy
double eps = 1e-5;
//PI constant
double PI = acos(-1);
//Enumerate triangle types as follows:
//Illegal triangle, acute triangle, equilateral triangle, isosceles triangle, right triangle, isosceles right triangle, obtuse triangle
enum TriangleType{NOT_ ANGLE,ACUTE_ TRIANGLE,REGULAR_ TRIANGLE,ISOCELES_ TRIANGLE,
RIGHT_ TRIANGLE,ISOCELES_ RIGHT_ TRIANGLE,OBTUSE_ TRIANGLE};
/ *
Function: judge the type of triangle according to the length
Parameters:
a. The three sides of B, C triangle
return:
The type of triangle. See triangle type
explain:
The cosine theorem is applied
cosA = (b^2 + c^2 - a^2)/2bc
* /
TriangleType getTypeOFTriangle(double a,double b,double c)
{
//Degrees of angles corresponding to edges a, B, C (radian system)
double angle_ A,angle_ B,angle_ C;
//Trilateral length must be positive
if(a
Given that the sum of the first n terms of the sequence is Sn, A1 = 2, the square of 2Sn = 2ansn an (n ≥ 2), find the sum of an and Sn
Because s (n + 1) - S (n) = a (n + 1), according to the meaning of the title: 2S (n + 1) ^ 2 = 2A (n + 1) s (n + 1) - A (n + 1), substituting the above formula into this formula: 2S (n + 1) ^ 2 = 2 [S (n + 1) - S (n)] s (n + 1) - S (n + 1) + s (n), so s (n) - S (n + 1) = 2S (n) s (n + 1), dividing both sides by s (n) s (n + 1) at the same time, we get: 1 / S (n + 1) - 1 / S (n) = 2
Unit conversion
Length Conversion
1 km = 1 000 m 1 m = 10 decimeters
1 decimeter = 10 cm 1 meter = 100 cm
1 cm = 10 mm
Area Conversion
1 sq km = 100 ha
1 ha = 10000 M2
1 square meter = 100 square decimeter
1 square decimeter = 100 square centimeter
1 sq cm = 100 sq mm
Volume (volume) product unit conversion
1 cubic meter = 1000 cubic decimeter
1 cubic decimeter = 1000 cubic centimeter
1 cubic decimeter = 1 liter
1 cc = 1 ml
1 cubic meter = 1000 liters
Conversion of weight unit
1 ton = 1000 kg
1kg = 1000g
1kg = 1kg
Conversion of RMB units
1 yuan = 10 Jiao
1 jiao = 10 points
1 yuan = 100 points
time conversion
1 century = 100 years 1 year = December
Big month (31 days): January, March, may, July, August, October, December
Small month (30 days): April, June, September and November
The average year is 28 days in February and leap year is 29 days in February
There are 365 days in a normal year and 366 days in a leap year
1 day = 24 hours, 1 hour = 60 minutes
1 minute = 60 seconds 1 hour = 3600 seconds
1、 Length
（1） What is length
Length is a measure of one-dimensional space
（2） Common unit of length
*Km * m * DM * cm * mm * um
（3） Conversion between units
*1 mm = 1000 μ m * 1 cm = 10 mm * 1 decimeter = 10 cm * 1 m = 1000 mm * 1 km = 1000 m
2、 Area
（1） What is area
Area is the size of the plane occupied by the object. The measurement of the surface of a solid object is generally called surface area
（2） Common unit of area
*Square millimeter * square centimeter * square decimeter * square meter * square kilometer
（3） Conversion of area units
*1 square centimeter = 100 square millimeter * 1 square decimeter = 100 square centimeter * 1 square meter = 100 square decimeter
*1 hectare = 10000 square meters * 1 square kilometer = 100 hectares
3、 Volume and volume
（1） What is volume, volume
Volume is the amount of space an object occupies
Volume, the volume of a box, oil bucket, warehouse, etc., usually called their volume
（2） Common units
1 volume unit
*Cubic meter * cubic decimeter * cubic centimeter
2 volume units * L * ml
（3） Unit conversion
1 volume unit
*1 cubic meter = 1000 cubic decimeter; * 1 cubic decimeter = 1000 cubic centimeter
2 volume units
*1 liter = 1000 ml; * 1 liter = 1 cubic meter; * 1 ml = 1 cubic centimeter
4、 Quality
（1） What is quality
Mass is the weight of an object
（2） Common units
*Ton t * kg * g
（3） Common conversion
*One kilogram; * one kilogram = 1000
5、 Time
（1） What is time
A period of time with a starting point and an ending point
（2） Common units
Century, year, month, day, hour, minute and second
（3） Unit conversion
*1 century = 100 years; * 1 year = 365 ordinary years; * 1 year = 366 leap years
*1、 Three, five, seven, eight, ten and twelve are the big moon, which has 31 days
*4、 June, September and November are the small moon, which has 30 days
*There are 28 days in February of a normal year and 29 days in February of a leap year
*Seconds = 24 minutes * 1 hour = 60
6、 Currency
（1） What is money
Money is a special commodity that acts as the equivalent of all commodities. Money is the general representative of value and can buy any other commodity
（2） Common units
*Yuan * Jiao * Fen
（3） Unit conversion
*1 yuan = 10 Jiao * 1 jiao = 10 Fen
C language: finding the area of triangle
According to the input three sides of the triangle, judge whether it can form a triangle, if it can output its area and type (isosceles, equilateral, right angle, ordinary). Write the program according to the requirements. It is required to write in simple C language!
Then somebody's dream had come true now. / * according to the three sides of the input triangle, judge whether it can form a triangle, if it can, output its area and type (isosceles, equilaterals, right angles, ordinary). Write the program according to the requirements. Write it in simple C language! * / # include # include main() {double
In the sequence an, A1 = 1. When n is greater than 2, the first n terms and Sn satisfy the square of Sn = an (sn-1 / 2) to find the general term of the sequence an
Sn²=an（Sn-1/2）
an=Sn-Sn-1
Sn²=（Sn-Sn-1）（Sn-1/2）
=Sn²-SnSn-1-1/2*Sn+1/2*Sn-1
SnSn-1=-1/2(Sn-S-1)
2SnSn-1=Sn-1-Sn
Divide both sides by snsn-1 at the same time
（1/Sn）-（1/Sn-1）=2
Because S1 = 1
S2=1/3
So 1 / Sn is an arithmetic sequence with the first term of 1 and the tolerance of 2
1/Sn=2n-1
Sn=1/2n-1
Sn-1=1/2n-3
｜ an = sn-sn-1 = (1 / 2n-1) - (1 / 2n-3) (general division can be considered)