Make a triangle with points a (1,0), B (2,0) and C (1,3) as vertices in the plane rectangular coordinate system. (1) calculate the area of triangle ABC; (2) Set triangle ABC Add 2 to the abscissa of the three vertices to find the area of the new triangle; (3) Add 1 to the ordinates of points a, B and C to obtain the area of the new triangle; (4) The coordinates of the three vertices of triangle ABC are expanded to twice the original, and the area of the new triangle is obtained

Make a triangle with points a (1,0), B (2,0) and C (1,3) as vertices in the plane rectangular coordinate system. (1) calculate the area of triangle ABC; (2) Set triangle ABC Add 2 to the abscissa of the three vertices to find the area of the new triangle; (3) Add 1 to the ordinates of points a, B and C to obtain the area of the new triangle; (4) The coordinates of the three vertices of triangle ABC are expanded to twice the original, and the area of the new triangle is obtained

（1）S= 1*3/2=3/2
(2) S= 1*3/2=3/2
(3) S= 1*3/2=3/2
(4) Two times of coordinate expansion is equal to two times of rectangular edge expansion, so the area is expanded by four times, so s = 3 / 2 * 4 = 6

If the length of the three median lines of the triangle is 5cm, 4cm and 3cm respectively, the area of the triangle is______

If the length of the three median lines of the triangle is 5cm, 4cm and 3cm respectively, the area of the triangle is 24cm ²

Vertex coordinate formula of quadratic function

Abscissa: - B / 2A ordinate: 4ac-b2 / 4A

Recently, I want to learn the limit. I want to ask what mathematical concepts I generally need to master under the limit. Do I need to know the formula of trigonometric function? I haven't touched mathematics for a long time. I hope the person who knows will explain it in detail,

It is mainly some limit operation formulas and four basic limits, and it is good to understand the concept. As for trigonometric functions, they are basically unnecessary in the limits

The vertex coordinates and maximum values of quadratic functions use a formula B / - 2A, 4ac-b * 2 / 4A, and how to find the value range of trigonometric functions?

Yes, the coordinates of the vertex of the quadratic function are (B / - 2A, 4ac-b * 2 / 4A), and the maximum value is the y value of the vertex
The value domain of trigonometric function can be calculated according to the definition domain combined with the image of trigonometric function

What is the limit formula of trigonometric function limx - > 0 (xsin3 / x)?

0≤|x*sin(3/x）|≤|x|
lim(x->0) x*sin(3/x）=0
[infinitesimal (x) * bounded (sin (3 / x)) = infinitesimal]