Let the minimum angle in △ ABC be a, and cosa = A-1 / A + 1, then the value range of a is_____ .

Let the minimum angle in △ ABC be a, and cosa = A-1 / A + 1, then the value range of a is_____ .

0＜A≤60
0.5≤cosA＜1
0.5≤a-1/a+1＜1
a≥3

Given that sina is the root of equation 6x = 1 - √ x, find (COS (a-5 π) * Tan (2 π - a)) / (COS (3 π / 2) * cot (π - a))
If I don't understand the title, I can send pictures

6X = 1 - √ x √ x = 1-6x x x = 36x ^ 2-12x + 1 36x ^ 2-13x + 1 = 0 (9x-1) (4x-1) = 0, x = 1 / 4, x = 1 / 9, x = 1 / 4 is root increasing, so Sina = 1 / 9 cosa = ± √ [1 - (Sina) ^ 2] = ± 4 √ 5 / 9 Tana = ± √ 5 / 20 cos (a-5 π) Tan (2 π - a) / cos (3 π / 2-A) cot (π - a) = cos (a-5

Trigonometric ratio
In triangle OAB, O is the origin coordinate, a (1, cos θ), B (sin θ, 1), θ ∈ (0, π / 2)], then when the area of triangle OAB reaches the maximum, the value of θ is ()
A π/6 B π/4 C π/3 D π/4
Write down the process ~ thank you

It should be to find the minimum area, select d passing through point a as AC, parallel to X axis, intersect with OB at point CC, the ordinate of point CC is cos θ, and it is on the straight line ob, so we can write its horizontal sitting is sin θ cos θ AC = - 1-sin θ cos θ s (OAB) = (1 / 2) * ac * 1 = (1 / 2) (1-sin θ cos θ) = (1 / 2) (1 - (sin2 θ / 2)) > = (1 / 2) (1-1

Given Tan (π 4 + α) = 12, the value of sin2 α − Cos2 α 1 + Cos2 α is ()
A. -53B. -56C. -16D. -32

∵ Tan (π 4 + α) = Tan π 4 + Tan α 1 − Tan π 4tan α = 1 + Tan α 1 − Tan α = 12, ∵ 3tan α = - 1, the solution is tan α = - 13; ∵ sin2 α − Cos2 α 1 + Cos2 α = 2Sin α cos α − Cos2 α 2cos2 α = Tan α - 12 = - 13-12 = - 56

Dissolve 5 grams of sugar in 20 grams of water. What's the percentage of sugar in the water
Don't take what's 100% as much as the score and process

Sugar in sugar water is sugar divided by sugar water
5/（5+20）=1/5

Dissolve 5 grams of white sugar in 50 grams of water and turn it into sugar water. How much is sugar? How much is water? How much is sugar?

How much sugar is the syrup?
5÷（5＋50）＝1/11
How many parts of sugar water is water?
50÷（5＋50）＝10/11
What fraction of water is sugar?
5÷50＝1/10

10 grams of sugar into 90 grams of water, sugar accounted for 30% of the water___ Sugar is the main component of sugar water___ (fill in the score)

The answer is: 19110