1、 In △ ABC, a: B: C = 1:1:2, a, B and C are opposite sides of a, B and C respectively, then in the following relation, the correct one is () A.a² = b²+ c² B.b² = a² + c² C.3a² = 2c² D.2a² = c² 2、 There are four triangles as follows: ① The ratio of ABC is 9:40:41 ② The ratio of ABC is 11:60:61 ③ The ratio of ABC is 1:2:3 ④ The ratio of ABC is 1:3:5 Where is a right triangle is () A.② B.①③ C.②③④ D.①②③ 3、 If one right side of a right triangle is 20cm and the hypotenuse is 25cm, the height of the hypotenuse is A.12cm B.6cm C.9cm D.15cm 4、 If the hypotenuse length of a right triangle is 5 cm and the perimeter is 12 cm, the area of the right triangle is 5 cm A.12cm² B.6cm² C.8cm² D.10cm² 5、 In △ ABC, ∠ C = 90 °, the length of its three sides is expanded by the same multiple, and the resulting triangle is () A. Right triangle B. it could be an acute triangle C. It can be an obtuse triangle D. It can't be a right triangle 6、 If the perimeter of a right triangle is 56cm and the length of its hypotenuse is 25cm, then the area of the right triangle is_____ cm² 7、 It is known that: B = 2m, a + C = 2m & sup2;, AC = m ^ 4 - 1, and M > 1 A. It must be an equilateral triangle B. it must be an isosceles triangle C. It must be a right triangle D. the shape is uncertain

1、 In △ ABC, a: B: C = 1:1:2, a, B and C are opposite sides of a, B and C respectively, then in the following relation, the correct one is () A.a² = b²+ c² B.b² = a² + c² C.3a² = 2c² D.2a² = c² 2、 There are four triangles as follows: ① The ratio of ABC is 9:40:41 ② The ratio of ABC is 11:60:61 ③ The ratio of ABC is 1:2:3 ④ The ratio of ABC is 1:3:5 Where is a right triangle is () A.② B.①③ C.②③④ D.①②③ 3、 If one right side of a right triangle is 20cm and the hypotenuse is 25cm, the height of the hypotenuse is A.12cm B.6cm C.9cm D.15cm 4、 If the hypotenuse length of a right triangle is 5 cm and the perimeter is 12 cm, the area of the right triangle is 5 cm A.12cm² B.6cm² C.8cm² D.10cm² 5、 In △ ABC, ∠ C = 90 °, the length of its three sides is expanded by the same multiple, and the resulting triangle is () A. Right triangle B. it could be an acute triangle C. It can be an obtuse triangle D. It can't be a right triangle 6、 If the perimeter of a right triangle is 56cm and the length of its hypotenuse is 25cm, then the area of the right triangle is_____ cm² 7、 It is known that: B = 2m, a + C = 2m & sup2;, AC = m ^ 4 - 1, and M > 1 A. It must be an equilateral triangle B. it must be an isosceles triangle C. It must be a right triangle D. the shape is uncertain

1, d.2a & sup2; = C & sup2; 2, ① the ratio of the three sides of △ ABC is 9:40:41, ② the ratio of the three sides of △ ABC is 11:60:61, which is a right triangle 3, d.15cm4, b.6cm & sup2; 5, A. right triangle 6. If one side of the right triangle is long a and the other side is long b, then the area of the right triangle = 0.5 * a * Ba ^ 2 + B ^ 2 =

Among the following household appliances and communication equipment, those that do not work with electromagnetic waves are ()
A. Refrigerator B. microwave oven C. mobile phone D. TV set

A. Refrigerators use the principle of heat absorption and heat release when the state of matter changes, so a does not use electromagnetic wave; B, microwave oven uses microwave to make water molecules in food vibrate and heat food, so it uses electromagnetic wave; C, mobile phone uses radio wave to transmit signal, so C uses electromagnetic wave; D, TV uses electromagnetic wave to transmit image signal and sound signal So choose a

To solve the fractional equation 2x + 1 + 3x − 1 = 6x2 − 1, the wrong step in the following four steps is ()
A. The simplest common denominator of the fractions on both sides of the equation is x2-1b. The integral equation 2 (x-1) + 3 (x + 1) = 6C is obtained by multiplying (x2-1) on both sides of the equation. The solution of the integral equation is x = 1D. The solution of the original equation is x = 1

If both sides of the fractional equation are multiplied by the simplest common denominator (x + 1) (x-1), we can get 2 (x-1) + 3 (x + 1) = 6, and the solution is x = 1. When x = 1, substitute x2-1 = 0, so x = 1 is an increasing root. The original equation has no solution, so D

Microwave oven is a kind of household appliance related to electromagnetic wave. It is convenient and fast to heat food with microwave oven
1. Metal tableware can be used in the microwave oven
2. Dry food is not easy to heat in the microwave oven 3. The glass door of the microwave oven will leak a lot of microblogs 4. Don't dry cloth in the microwave oven

2 and 4 are correct

1. In the formulas,,,,,, the number of fractions is ()
A. 2 B, 3 C, 4 D, 5 d
2. Given that hyperbola y = (K ≠ 0) passes through point (3,1), then it also passes through point ()
A．（ ,-9） B．（-1,3） C．（-1,-3） D．（6,- ）
Y = K / X - 1 / 2) a answer (1 / 3, - 9)

There is no formula for the first question
The second question is y = K / X. take x = 3 and y = 1
1=K/3 K=3
So y = 3 / X
Then take them in one by one. Finally, choose C

How to explain microwave and electromagnetic wave?

What is microwave
Microwave is a kind of radio wave with high frequency and short wavelength, which is similar to the electromagnetic wave received by ordinary TV and radio and the ultraviolet light wave emitted by ultraviolet lamp. Microwave itself does not generate heat. However, when microwave makes polar molecules such as water, oil, sugar and protein in food rub against each other, it will generate heat, just as we rub our hands quickly, It's the same as fever
What is electromagnetic wave? How many kinds of electromagnetic wave are there? Does it affect human body?
From a scientific point of view, electromagnetic wave is a kind of energy. Any object that can release energy will release electromagnetic wave. Electricity and magnetism can be said to be one and two sides. Changing electricity will produce magnetism, and changing magnetism will produce electricity. The change of electromagnetic wave is just like the water wave generated by the breeze on the water surface, so it is called electromagnetic wave, and the number of changes per second is frequency
When the frequency of electromagnetic wave is low, it can be transmitted mainly by a tangible conductor; when the frequency gradually increases, the electromagnetic wave will overflow to the outside of the conductor, and it can transmit energy without medium. This is a kind of radiation. For example, the distance between the sun and the earth is very far, but when we are outdoors, we can still feel the light and heat of warm sunshine, This is like the principle that electromagnetic radiation transfers energy through radiation phenomenon
Electromagnetic radiation is a way to transfer energy. There are three kinds of radiation
1. Ionizing radiation
2. Non ionizing radiation with thermal effect
3. Non ionizing radiation without thermal effect
The energy of electromagnetic wave is directly proportional to the frequency. When the high energy electromagnetic wave transmits the energy to other substances, it may collide with the electrons of atoms and molecules in the substance, and make the substance full of charged ions. This effect is called "dissociation", and the electromagnetic wave causing this dissociation phenomenon is called dissociation radiation, including gamma ray, X-ray, ultraviolet ray, etc
Both electromagnetic waves and infrared rays entering the visible light frequency can not cause dissociation effect, which is called non dissociative radiation. Here, we must clarify the concept that radiation damage refers to dissociative radiation (dissociative radiation will snatch electric charges with substances in the body and produce ions to destroy physiological tissues), while non dissociative radiation does not have dissociative ability and will not produce free ions harmful to human body, A large number of non free electromagnetic waves can only cause thermophilic effect
It's like sunbathing or standing under a light bulb. As long as we don't transmit too much energy to the human body in a short period of time, physiological tissues can regulate it. Therefore, receiving non free electromagnetic waves for a long time in a safe range will not cause cumulative damage. Q2: will we be exposed to electromagnetic waves in our daily life?
In our living environment, "electricity" and "magnetism" are ubiquitous. In addition to the sunlight and lightning of nature, all kinds of electrical appliances, such as television, microwave ovens, light bulbs, computers, and even radio electromagnetic waves from radio stations, television stations, amateur radio stations, radio taxis, police radio stations or satellite mobile communications, exist in our living environment

If the height on the bottom of an isosceles triangle is 1 and the angle between the height and the waist is 60 degrees, then the area of the triangle is 1
A. 3 B. root 3 / 2 C. 2 times root 3 D root 3

If you know that when the angle of a right triangle is 60 degrees, 30 degrees and 90 degrees, the side corresponding to 30 degrees is half of the side corresponding to 90 degrees (i.e. hypotenuse), then you know that the side corresponding to 30 degrees (i.e. height) is 1, and the side corresponding to 90 degrees (i.e. waist) is 1x2 = 2
According to Pythagorean law, it can be concluded that the side corresponding to 60 ° is 2 & # 178; - 1 & # 178; = 4-1 = 3, which is (radical) 3
Then we can get the formula of the base of isosceles triangle, then the base is (root sign) 3x2 = 2 times (root sign) 3
Because the height of the bottom is 1, we can get △ s isosceles triangle = 1x2 times (root sign) 3 △ 2 = (root sign) 3
So everyone knows the answer

Some household appliances will be damaged if the temperature is too high during use
A. Electric cooker B. electric water heater C. electric iron D. TV set

Some electrical appliances use electric heating, but some electrical appliances need to prevent excessive heating. For example, electric rice cookers, electric water heaters and electric irons all use electric heating, while TV sets need to prevent overheating and causing harm to TV sets

A. B, C and D broke the glass when they played football. A said, "C or D broke it." B said, "d broke it." C said, "I didn't break the glass." d said, "I didn't break it." only one of them lied. Which one of them broke the glass?

"B said," d broke it. "D said," I didn't break it
The two contradicted each other, so one of them lied
So "C said," I didn't break the glass. It's true. The glass wasn't broken by C
Because a says, "C or D broke it." it's true
Then the glass can only be broken by D

The following electrical appliances do not use electric heating to work: a electric iron B TV C rice cooker D electric iron

B TV
If the soldering iron needs to melt the solder, it must be hot
The rice cooker also needs to be heated. It's not necessary to say that it's Gejiu
I haven't heard of that person touching the electric iron at work
The answer is so obvious