In the isosceles trapezoid ABCD, AD / / BC, ad = DC = AB, BD = BC. Find the degree of angle a? (it's better to have a process)

Let ∠ abd = X
∵AB=AD
∴∠ADB=∠ABD=x
∵AD//BC
∴∠DCB=x
∵AB=CD
∴∠C=∠ABC=2x
∵BD=BC
∴∠BDC=∠C=2x
∵∠ADC+∠C=180°
∴x+2x+2x=180,x=36
Therefore, a = 180-2 * 36 = 108 degree

A + 1 / 2 of a = 8 find the value of a square + 1 / 2 of a

The square of a + A is equal to the square of 8
The square of a + 2 + 1 / 2 of a equals 64
The square of a + one square of a equals 64-2 equals 62

C + + problem, write a program to calculate the surface area and volume of the ball, cylinder and cone
#include
#include
using namespace std;
#define PI 3.1415
class circle
{
public:
\x09void information()
\x09{\x09
\x09\x09double a;
\x09\x09couta;
\x09}
};
class sphere:public circle
{
public:
void first(double s1,double a)
\x09{
\x09\x09double v1;
\x09\x09s1=4PIaa;
//The first and second mistakes
v1=(PIaaa*4)/3；
cout

There are more than a few mistakes in your program. It's just terrible. I simply modified it and compiled it. #include & nbsp; & lt; iostream & gt; #include & nbsp; & lt; string & gt; using & nbsp; namespace & nbsp; STD; #define & nbsp; PI & nbsp; 3.1415class & nbsp; circle {P

A rectangle, half a meter long and three fifths wide, has a circumference of () meters and an area of () square meters

Perimeter = 2 * (1 / 2 + 3 / 5) = 2 * 11 / 10 = 11 / 5 = 2.2m
Area = 1 / 2 * 3 / 5 = 3 / 10 = 0.3 M2

According to the requirements in brackets, use the rounding method to take the approximate value of 1022.0099, where the error is (a.1022.01 is accurate to 0.01)
B. The third power of 1.0 * 10 (retain two significant digits) c.1022.010 (accurate to the thousandth digit) d.1020 (accurate to the tenth digit)
Which question should I choose? Why?

A. 1022.01 to 0.01
This is accurate to 0.1

A train is 300 meters long. It goes through the 300 meter long tunnel at the speed of 60km / h. how many seconds does it take for the train to enter the tunnel and go through the tunnel completely?

Speed = 60 △ 3.6 = 50 / 3m / S
Time = (300 + 300) △ 50 / 3 = 36 seconds

As shown in the figure, the quadrilateral ABCD is inscribed in circle O, BD is the diameter, AE is vertical to CD, the perpendicular foot is e, Da bisects ∠ BDE, and verify that AE is the tangent of circle o

It's very simple
Because Da score ∠ BDE, so ∠ BDA = ∠ EDA
Because od = OA, ∠ oad = ∠ ODA
So ∠ oad = = ∠ EDA
So OA is parallel to ed
Because AE vertical CD
So AE vertical OA
So AE is the tangent of circle o

Why is the speed of electric current equal to the speed of light

The electric field is not an electromagnetic wave, but a material form
But it builds speed at the speed of light
The essence of light is electromagnetic wave, which is different from electric field and magnetic field

There are two charging methods for mobile phone: 1. Pay 20 yuan monthly rent, and then charge 0.18 yuan per minute. 2. No monthly rent, 0.28 yuan per minute
Q: how many minutes do you call each month? The charges of the two billing methods are exactly the same

Let's assume that the cost of X minutes is the same
20+0.18X=0.28X
X=111.11~

In the square ABCD, the length of DM is obtained by crossing point D as DP, AC at point m, AB at point n, and the extension of CB at point P, if Mn = 1, PN = 3

∵AB‖CD
∴AM/AC=MN/MD
∵AD‖BC
∴AM/MC=DM/MP
∴MN/MD=DM/MP
∴MD²=MN*MP=1*4=4
∴MD=2
If you don't know, ask again,

In the isosceles trapezoid ABCD, AD / / BC, ad = DC = AB, BD = BC. Find the degree of angle a? (it's better to have a process)