Double angle proof of Tan What formula should be used for Tan & Ө / 2 - 1 / Tan & Ө / 2 = 2 / Tan & Ө?

Double angle proof of Tan What formula should be used for Tan & Ө / 2 - 1 / Tan & Ө / 2 = 2 / Tan & Ө?

What do you mean? I can't express it, so I use a instead
Well, using the double angle formula
tana=2tan（a/2）/（1-tan²（a）/2）
1/tana=【1-tan²（a）/2】/2tan（a/2）
2/tana=【1-tan²（a）/2】/tan（a/2）
Take you as Tan (A / 2) - 1 / Tan (A / 2) = [1-tan & sup2; (a) / 2] / Tan (A / 2)
Therefore, it is proved that Tan & / 2 - 1 / Tan & / 2 = 2 / Tan &

Tan angle a equals 7. What is the angle a?

81.8698

Who knows how many degrees Tan α = 2 α is
What does α = arctan2 mean?

α=arctan2

In the triangle ABC, if angle B = 45 °, angle c = 30 ° and BC = 10, then AB = () is accurate to 0.1

Make ad perpendicular to d
Let BD = x, then ad = x CD = x / tan30 = root 3x
BD+CD=10
Find x 10 (radical 3-1) / 2
AB = root 2 x
=5.2

Ask about the trigonometric function of acute angle in the third year of junior high school
It is known that in △ ABC, ∠ C = 90 °, sinA:sinB=4 : 5, then the value of sina is?
Depressed ah, what problem - no ~ master help to solve the next process also write it down, thank you

4^2+5^2=41
Sina = 4 / radical 41

Solving a problem of trigonometric function with acute angle
In △ ABC, ∠ C is the largest angle, and ∣ sin ^ 2a-1 / 2 ∣ + (2cos ^ 2b-1) ^ 2 = 0. Try to determine the shape of △ ABC

∣ sin ^ 2a-1 / 2 ∣ + (2cos ^ 2b-1) ^ 2 = 0 ∣ sina-1 / 2 = 0 2cosb-1 = 0 ∣ Sina = radical 2 / 2, CoSb = radical 2 / 2 or CoSb = - radical 2 / 2 (because ∠ C is the largest angle, so ∠ A and ∠ B can not be obtuse angle, so it is omitted) ∣ a = 45 °, B = 45 °

Solution of sharp angle trigonometric function
[calculation process required] in triangle ABC, angle c = 90 °, tanb = 2, a = 4, then what are B and C equal to?

Mark the letter anticlockwise. Tamb = AC / BC = 2, so AC = b = 8. Using Pythagorean theorem, ab = C = (the square of 8 + the square of 4) open root = root (80)

The problem of sharp angle trigonometric function
In △ ABC, the angle c = 90 ° and AC greater than BC, CD ⊥ AB in D, de ⊥ AC in E, EF ⊥ AB in F, if CD = 4, ab = 10, then EF: AF is equal to ()
A. 1:1 B. radical 5:2 C. radical 5:5 D.2 × radical 5:5
I'm so worried

According to the law of photography, Pythagorean theorem and similarity, we can calculate D
BD = 2-fold root 5 AC = 4-fold root 5 DC = 8 BD = 2 CE = 4 / 5-fold root 5 de = 8 / 5-fold root 5 AE = 16 / 5-fold root 5 triangle AEF has a similarity ratio of 2-fold root 5 to 5
That's about it. It's a lot of trouble

Triangle ABC is inscribed on circle O, angle c is equal to 45 degrees, what is the radius of circle O?

The conditions you give are not enough. If an angle is fixed, there can be countless triangles, so there are countless circumscribed circles

Known: as shown in the figure, △ ABC, AC = 10, sinc = 45, SINB = 13, ab

Take ad ⊥ BC at point D, as shown in the figure, in RT △ ADC, AC = 10, sinc = 45, ≁ ad = acsinc = 10 × 45 = 8, in RT △ abd, SINB = 13, ad = 8, then AB = adsinb = 24