Given Tana = 2, find the square of. 2sina minus 3sinacosa minus 2cos square

Given Tana = 2, find the square of. 2sina minus 3sinacosa minus 2cos square

∵tanA=2
∴2sin²A-3sinAcosA-2cos²A
=(2sin²A-3sinAcosA-2cos²A)/(sin²A+cos²A) 【sin²A+cos²A=1】
=(2Sin & # 178; a / cos & # 178; a-3sina / cosa-2) / (Sin & # 178; a / cos & # 178; a + 1) [divide up and down by cos & # 178; a]
=(2tan²A-3tanA-2)/(tan²A+1) 【sinA/cosA=tanA】
=(2×4-3×2-2)/(4+1)
=0

Is 2cos square x equal to the square of cos2x?
Is 2cos & # 178; X equal to cos2x & # 178;?

No
cos2x=2cos²x-1
So 2cos & # 178; X = 1 + cos2x

Prove (2cos square x-1) / 2tan (Pie / 4-x) * cos square (Pie / 4-x)
Say yes, help

It is proved that the left formula = cos2x / [2tan (Pie / 4-x) cos (Pie / 4-x) square] = cos2x / 2Sin (Pie / 4-x) cos (Pie / 4-x) = cos2x / sin2 (Pie / 4-x) = cos2x / sin (Pie / 2-2x) = cos2x / cos2x = 1 = right formula

English translation
I'm sorry to hear that your class lost the money needed for the new year's party. What's the matter now

I am sorry to know that your class has lost the money for the New Year's Party,how is it now?
Baidu education team [Haina Baichuan group] will answer for you. Please click the "select as satisfactory answer" button,

Oh, wrong. How many meters is one kilometer

1000

1 + 2 + 3 + 4 + 5. + 99 + 100 = several

1+2+3+4+5 .+99+100=
There are 100 numbers from 1 to 100
1+100=101 2+99=101 3+98=101
So 101x50 + 5050

Ask the meaning of two English words
Eversea and Neverland

Eversea
Neverland Neverland

In the arithmetic sequence an, given A2 + A4 + A6 = 12, A3A5 = 7, find A8
In the arithmetic sequence an, given A2 + A4 + A6 = 12, A3A5 = 7, find A8,

A2 + A4 + A6 = 3A4 = 12, so A4 = 4, let the equal difference be D, A3 = a4-d, A5 = A4 + D
A3A5 = (a4-d) (A4 + D) = 16-d * d = 7, so d = 3 or - 3
When d = 3
a4=a1+3d a1=a4-3d=4-9=-5
So A8 = a1 + 7d = - 5 + 3 * 7 = 16
When d = - 3
a4=a1+3d a1=a4-3d=4+9=13
a8=a1+7d=13-21=-8

Let z = sin XY find DZ

z= sinxy
dz = (cosxy) ( xdy + ydx)
-------------
z= sinxy
dz=d(sinxy)
= cosxy d(xy)
= cosxy (xdy +ydx)

A car consumes 2 liters of fuel for 25 kilometers. How many liters of fuel does it consume on average for one kilometer? How many kilometers can you drive per liter of fuel?

(1) 2 △ 25 = 0.08 (L). A: the average fuel consumption is 0.08 L for 1 km. (2) 25 △ 2 = 12.5 (km). A: the average fuel consumption per liter is 12.5 km