What are sin, cos, tan and their meanings

What are sin, cos, tan and their meanings

I've forgotten Tan cos sin - thank you and what's Tan cos sin,
I know I want the number of special corners,

tan30=√3/3 tan45=1 tan60=√3
sin30=1/2 sin45=√2/2 sin60√3/2
cos30=√3/2 cos45=√2/2 cos60=1/2
(√ is the root)

What function is f (x) = SGN (x)

When x is a positive number, f (x) is 1; when x is a negative number, f (x) is - 1; when x is zero, f (x) is 0

A square needs 5400 pieces of cement square bricks with a side length of 4 decimeters; how many pieces of cement square bricks with a side length of 6 decimeters?

Suppose that if the side length is 6 decimeters, X bricks are needed, 6 × 6x = 4 × 4 × 5400, & nbsp; 36x = 86400, & nbsp; & nbsp; & nbsp; X = 2400; a: 2400 bricks are needed

How to calculate 1 / 1 * 3 + 1 / 3 * 5 + 1 / 3 * 7 + 1 / 7 * 9 + 1 / 9 * 11? Why?

"1 / 3 * 7" should be "1 / 5 * 7"
1/1*3+1/3*5+1/5*7+1/7*9+1/9*11
=1/2*(1-1/3)+1/2*(1/3-1/5)+1/2*(1/5-1/7)+1/2*(1/7-1/9)+1/2*(1/9-1/11)
=1/2*(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)
=1/2*(1-1/11)
=1/2*10/11
=5/11

There are a series of points P1 (x1, Y1), P2 (X2, Y2) on the X and Y planes PN (xn, yn) for each natural number n, the point PN is located on the image of the function y = x & sup2; (x ≥ 0), the circle PN with the point PN as the center is tangent to the X axis, and the circle PN and the circle PN + 1 are circumtangent to each other, if X1 = 1, and xn + 1

Since the circle PN with the center of the circle PN is tangent to the X axis, the distance between the two centers is the sum of two Y values, so there are (xn-x (n-1)) & sup2; + (yn-y (n-1)) & sup2; = (yn + y (n-1)) & sup2;, (xn-x (n-1)) & sup2; = 4yny (n-1), X & sup2; n-2xn * x (n-1) + X (n-1) & sup2; = 4x & sup2; n

The coordinates of the center of the circle are all integers, the circle with radius of 5 passes through point a (- 2,6), and the chord length with m (5,4) as the midpoint is twice the root sign 5
Please give the detailed process, thank you

Analysis: if you want to write out the equation of a circle, you need to know the center and radius of the circle. The radius of the circle has been given in the question. You only need to work out the coordinates of the center of the circle. The coordinates of the center of the circle can be obtained by listing a system of quadratic equations with one variable. The distance between the center of the circle is the distance between the center of the circle and the midpoint of the chord. A is a point on the circle, M is the midpoint of the chord. The center distance is equal to the square of the radius minus the square of half the chord
Let the coordinates of the center of the circle be (a, b)
From the meaning of the title, we can see that the distance between the center of the circle D is twice the root sign 5
(a+2)^2+(b-6)^2=25
(a-5)^2+(b-4)^2=20
Solution of joint procedure group

Y = 4x ^ 2 + 16 / (x ^ 2 + 1) ^ 2 minimum value of function

a=2x,b=4/(x^2+1)
a^2+b^2>=2ab
When a = B, a ^ 2 + B ^ 2 = 2Ab is the minimum
2x=4/(x^2+1)
x^3+x-2=0
(x-1)(x^2+x+2)=0
X = 1, when x = 1,
Y = 4x ^ 2 + 16 / (x ^ 2 + 1) ^ 2min = 4 + 16 / 4 = 8

The value range of cosx = A-3 / 5 + A

-1=-4

The perimeter of a rectangular vegetable field is 184 meters, and its length is three times of its width?

Suppose the width is x meters, then the length is 3x meters. According to the meaning of the question, we can get the equation: 2 (x + 3x) = 184, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 8x = 184, & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; X = 23, then the length is 23 × 3 = 69 meters. A: the length and width of a rectangle are 69 meters and 23 meters respectively