As shown in the figure, line AB = 8cm, C is any point on the extension line of line AB, M is the midpoint of AC, and N is the midpoint of BC. Calculate the length of line Mn Make it clear

As shown in the figure, line AB = 8cm, C is any point on the extension line of line AB, M is the midpoint of AC, and N is the midpoint of BC. Calculate the length of line Mn Make it clear

NB=NC=BC/2,MA=MC=AC/2
MN=NA-MA=NB+AB-AC/2=NB+AB-(1/2)(AB+BC)=NB+AB-AB/2-BC/2=AB/2=8/2=4(cm)

Find the meaning of an English phrase
Under the four subheadings below means at least four subheadings or at most four,

First of all, you should make clear the usage of "below". Below is an adverb used as a post attributive to modify "subtitle"
That's the point
Under the four subheadings below (with four subheadings)

The sum of numerator and denominator is 23. After the denominator is increased by 19, a new fraction is obtained. This fraction is reduced to the simplest fraction, which is 15. What is the original fraction?

They are not in the same class

They are in the different class.

If the quadrilateral ABCD satisfies: [vector] AB + CD = 0, (AB + AD) * AC = 0, then the quadrilateral
Pay attention to the plus and minus sign

AB=-BD
==>A quadrilateral ABCD is a parallelogram
(AB-AD)*AC=0
DB*AC=0
The diagonal is vertical;
The quadrilateral ABCD is a diamond

Verb phrases

There are too many, which aspects? Take a few examples: wake up, get up, get dressed, go to bed, wash face, wash clothes, have breakfast / lunch / diner / super, have sports, play football / basketball / volleyball, go swimming / shopping

Let the center of gravity of triangle ABC be g, Ag = 6, BG = 8, CG = 10, then s △ ABC =?

Let BG intersect AC with D, extend BD to e, so that de equals DG, so we can prove that EC = Ag = 8, so GCE is a right triangle of 6810, and the rest is simple,
SBDC=SCEB-SCDE=48-12=36
SABC=36*2=72

Is glass countable
Is glass countable when making glasses
Can we say three glasses of?
Good answer. Yes, I will add 50 points

① You can't count on glass
② Three glasses of is OK
③ A pair of glasses

In RT triangle ABC, angle c is a right angle. Sina = two-thirds. Then tanb =?

Sina = 2 / 3, if the opposite side is 2a and the hypotenuse is 3a, then the other side is the root sign, and ((3a) ^ 2 - (2a) ^ 2) is (root sign 5) * a, and tanb = (root sign 5) / 2

how,you,do,his,name,spell?his,last,is,name,cooper
Conjunctions into sentences

How do you spell his name?
His last name is Cooper.
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