Mathematics Evaluation Handbook for Junior High School, Chemistry Evaluation Handbook for Junior Hig

The PC must be twice as CE's.

Proof: Crossing point C sits on an auxiliary line CF perpendicular to OA, and the vertical foot is F

OM is the angular bisector, AOM = BOM, and cf OA, CE OB, OCF = OCE

and oc=0c, triangle ocf triangle oce (corner corner).

cf=ce.

In a right-angled triangle, the angle BPC is 30 degrees, and the right-angled side of the 30-degree pair is half of the hypotenuse, and in the right-angled triangle PFC, the length of the PC is twice that of CF.

i.e. there must be twice as much CE as there is.

If you understand it, ask again if you don't understand, I wish you progress in your learning!!

According to your title, the PC must be larger than the CE.

Proof: Crossing point C sits on an auxiliary line CF perpendicular to OA, and the vertical foot is F

OM is the angular bisector, AOM = BOM, and cf OA, CE OB, OCF = OCE

and oc=0c, triangle ocf triangle oce (corner corner).

cf=ce.

In a right-angled triangle, the hypotenuse is greater than the right-angled side, and in the right-angled triangle PFC, pc cf

i.e. there is pc ce

I don't know if I misunderstood your topic.

3.Propylene and hydrochloric acid react, A and B do not react Description: C commits Lu Yuding h A B and B The compound solution put into C has propylene precipitation, indicating that Ding C.

A has precipitated in the compound solution of B, indicating that A B.

To sum it up, it's all about choosing item d.

4.The first question is fe3o4

b: The lightest gas is hydrogen (H2) The answer to the second question is clean energy (this answer is not the only one), and the third question and 3 answers are written as C co H2

Section 4 asks Fe+CuSo4==Cu+FeSo4 (displacement reaction) amount... I was lucky to die

(1) A group of two numbers can be divided into 50 groups, and the sum of each group is 1, so the result is 50

2) The principle is the same as the first question, every two numbers in a group, a total of 10 groups, each group sum is -3, so the result is -30

1. Let one polygon be an n-sided and the other is a 2n-sided shape, and the sum of the inner angles is (n-2)*180 (formula) and (2n-2)*180 respectively, so n-2:2n-2=1:3 Therefore, n=4, that is, the two are quadrilaterals and octagons 2, no, the sum of the inner angles of the pentagonal is (5-2)*180=540, each angle is 108, and 360 cannot be paved, that is, it is impossible to be closely paved on the ground (like the inner angle of a square, the inner angle of an equilateral triangle is 60, 60*6=). 360, both of which can be floored).

2. Yes, this is the content of the first session: dense shop, you can preview it!

Pentagons and decagons.

No. The inner angle of a regular pentagon is 108 degrees, which is not a fraction of the circumferential angle, and multiple vertex angles converge, leaving a gap. Orthogonal shapes can be spliced seamlessly.

Also the question on page 15:

Question 3 (Lesson 2): How to do it?

impracticable！I speak good English

13km A went 6*2=12km to the east, and B went 5*1=5km to the north

Using the Pythagorean theorem, 5*5=12*12=169=13*13 is obtained

So A and B are 13km apart

Set the whole journey x meters, A speed x 4, B speed x 5

x 4 - x 5) (x 5) = 1 4 = 25 percent