It can calculate 21.38 - (3 / 30 + 1.38) 6.8-3.9 * 4 / 13 + 2.8 It can be easily calculated 21.38 - (3 / 30 + 1.38) 6.8-3.9 * 4 / 13 + 2.8

It can calculate 21.38 - (3 / 30 + 1.38) 6.8-3.9 * 4 / 13 + 2.8 It can be easily calculated 21.38 - (3 / 30 + 1.38) 6.8-3.9 * 4 / 13 + 2.8

21.38 - (3 / 30 + 1.38)
=21.38-1.38-3 / 40
=16 and 37 / 40
There is no simple method for the second direct calculation

If cos140 ° = a, then the root sign is 1-sin square 400 °=

cos140=cos(180-40)=-cos40=a
cos40=-a
∵400
√(1-sin^2 400)
=√(1-sin^2 (360+40))
=√(1-sin^2 40)
=cos40
=-a

If the area of the rectangle is 16 times the root sign 3 and the angle between the diagonal and one side is 30 degrees, what is the area of the largest square that can be cut out of the rectangle

Let the width of the rectangle be x, and the length of the other side be the root sign 3 * X
That is, area = x * radical 3 * x = 16 radical 3
x=4.
Therefore, if the side length of the largest square is 4, the area is 4 * 4 = 16

Function problem, range, analytic expression, urgent!
1. Known function f (x) = LG (AX ^ 2 + ax + 1) Q1: if the domain of F (x) is r, find the value range of real number a Q2: if the domain of F (x) is r, find the value range of a
2. Given that the domain of the function y = LG [(a ^ 2-1) x ^ 2 + (a + 1) x + 1] is r, find the value range of the real number a

The domain of F (x) is r
ax^2 + ax + 1
A = 0 1 > 0 holds
A is not equal to 0 a > 0 a ^ 2-4a

If x tends to infinity, we can find the limit of &; 1 / [x &; sin &; 1 / (3x)]
X tends to infinity, find the limit of 1 / [x & # 178; sin & # 178; 1 / (3x)]

Let y = 1 / (3x), then the original formula = 9 * y * y / [sin (y) * sin (y)] is evaluated under the limit of Y tending to 0, and it can be solved by using Robita's law

The perimeter of a rectangular vegetable field is 264 meters, and the length is three times the width. What is the area of this vegetable field?

If the width is x, the length is 3x
If perimeter = 8x = 264, x = 33
So area s = 33x33x3 = 3267m ^ 2

Mathematics Evaluation Handbook Jiangsu Education Press sixth grade volume 2 page 14 question 3
How many square centimeters of cardboard should be used to make a column with a bottom circumference of 94.2 cm and a height of 10 cm?

94.2 × 10 = 942 (cm2)
R = 94.2 △ 6.28 = 15 (CM)
3.14 × 15 square × 2 = 706.5 (square centimeter)
942 + 706.5 × 2 = 2355 (cm2)

What is the general solution of dy / DX = e ^ (X-Y)

Separate variable e ^ YDY = e ^ xdx and seek integral e ^ y = e ^ x + C Y = ln (e ^ x + C)

How many spelling methods are there to put 24 small squares with a side length of 1cm into a large rectangle? Please draw a sketch on the checkered paper below and calculate the perimeter of the large rectangle in each spelling

The figure is as follows: (1) (24 + 1) × 2 = 50 (CM); (2) (2 + 12) × 2 = 28 (CM); (3) (3 + 8) × 2 = 22 (CM); (4) (4 + 6) × 2 = 20 (CM)

The perimeter of the bottom surface of the five cylindrical columns is 25.12 decimeters and the height is 6 meters. The surface of these columns is painted with an average of 0.5 kg of paint per square meter

The side area of 5 cylindrical columns needs painting
=0.5×2.512×6×5
=37.68kg