In the triangle ABC, ab = AC = 13, BC = 10, point D is the midpoint of BC, de ⊥ AB, and the perpendicular foot is point E, then what is de equal to?

In the triangle ABC, ab = AC = 13, BC = 10, point D is the midpoint of BC, de ⊥ AB, and the perpendicular foot is point E, then what is de equal to?

Because AB = AC, point D is the midpoint of BC
So BD = DC = 1 / 2, BC = 5, ad ⊥ BC (three wires in one)
In RT △ ADC, AD & # 178; + DC & # 178; = AC & # 178;
AD=12
S△ABD=1/2 *AB*DE=1/2 *BD*AD
DE=60/13

As shown in the figure, in the isosceles triangle ABC, AB equals AC equals 13, BC equals 10, D is the midpoint on BC, and Mn is the moving point on AD and ab respectively, then the minimum value of BM plus Mn is --------
As shown in the figure, in the trapezoidal ABCD, CD is equal to one, Mn bisects CD vertically, intersects AB at point m, intersects CD at point n, extends CD, folds rectangular paper ABCD so that point d falls on point P on Mn, and calculates the square area with point P as the side length

Minimum 5

As shown in the figure △ ABC, D is the point on AB, and AC = dB, CE bisects ad, ∠ ADC = ∠ ACD, CE = a, then BC =?

Solution
DF ‖ AC through D
∵∠ADC=∠ACD
∴AC=AD
∵AC=DB
∴AD=DB
∴AB=2DB
∵DE∥AC
∴DB/AB=DF/AC
∴DF=AC/2
CE split ad equally
∴ED=AD/2
∵AD=AC
∴ED=DF
∵DE∥AC
∴∠CDF=∠ACD
∴∠CDF=∠ADC
∵CD=CD
The ∧ EDC is equal to the ∧ FDC
∴CF=CE
∵DE∥AC
∴BF/BC=DB/AB
∴BF/BC=1/2
∴BF=CF
∴BC=2CF
∴BC=2CE=2 a

As shown in the figure, ad is the middle line of △ ABC, ∠ ADC = 45 ° turn △ ADC along the straight line ad, and point C falls on C '. Try to explain the reason why c'b > DC

The main test points of this problem are: 1, find ∠ c'db =?; 2, the longest inner hypotenuse of a right triangle
Know CD = c'd, ∠ ADC = ∠ bad + ∠ abd; and ∠ ADC = 45 ° (here is the key)
Therefore, in the triangle c'bd formed after folding, DC = c'd; c'db = 180 ° - (45 ° + 45 °) = 90 °
We know that the enclosed figure is a right triangle, c'b is a hypotenuse, c'b > DC ', so c'b > DC,

In the triangular pyramid s-abc, △ ABC is an equilateral triangle with side length 4, plane sac ⊥ plane ABC, and SA = SC = 2, radical 3
In a triangular pyramid s-abc, △ ABC is an equilateral triangle with four sides

If ∵ plane sac ⊥ plane ABC, then SS & # 39; ⊥ plane ABC is obtained naturally
And as = CS = 2 √ 3, CS & # 39; = 2
In RT △ SS & # 39; C
∴SS'=2√2,
I don't know what you want,
If it is volume: bottom area (s △ ABC) * height (SS & # 39;) = (1 / 2) * AB * sin60 ° * BC & nbsp; & nbsp; * & nbsp; SS & # 39; = 8 √ 6

In a triangular pyramid s-abc, △ ABC is an equilateral triangle with side length 4, the plane sac is perpendicular to the plane ABC, SA = SC = 2 times the root 3, and D is the midpoint of ab

In △ sac, SA = SC, Se ⊥ AC, AE = CE = 2, the right side of the right triangle CES is SE = double root 2. Because plane sac is perpendicular to plane ABC and Se ⊥ AC, se is perpendicular to plane ABC, so se ⊥ De

If the distance between a, B, C and plane α is equal and a is not on the same line, then

Then point B does not belong to α,
And point C does not belong to plane α

If there are three non collinear traces on plane a and the distances of plane B are equal, then a / / b. is it right or wrong? Why?
As the title, the best picture

No, a and B can be intersecting planes, which means that there can be countless points with the same distance from B

Is there any point in the same plane which is equidistant from any three points on a straight line? If so, what are the characteristics of these four points?

After taking any three points, connect the three points to get a triangle. Make the vertical bisectors of any two sides of the triangle intersect at a point, which is the fourth point

What is the number of points with equal distance to three points a, B and C on the plane
A. Three
B. Two
C three or more
D one or none
Please explain why,
Change answer a to one

D this is a test of logical reasoning, you can use a special method: assuming that three points are collinear, then there is no point, assuming that three vertices of an equilateral triangle, then there is one, other can not think of
Special law is a very important method in middle school