Sine value of trigonometric function Compare the following sine values (1) SiN4 π / 7 and sin5 π / 7 (2) sin (- 3 π / 5) and sin (- 4 π / 5)

Sine value of trigonometric function Compare the following sine values (1) SiN4 π / 7 and sin5 π / 7 (2) sin (- 3 π / 5) and sin (- 4 π / 5)

Sin5 π / 7 large
Sin (- 3 π / 5) large

The relationship between trigonometric function and sine
Ask the relationship between the following values:
Sin 2 α and sin α
Cos2 α and cos α
Tan 2 α and Tan α
Note that the above relationship can only be expressed by one value. For example, given sin α, find sin2 α

If sina is known, use the sum of the squares of sina and cosa to find cosa, and then sin2a = 2sinacosa
Cos2a = the square of cosa - the square of sina
Tan2a = (2tana) / (the square of 1-tana)

What is the sine value of trigonometric function at 22.5 ℃

0.3826834323650897717284599840304

Passenger cars travel 80 kilometers per hour, and freight cars travel 95 kilometers per hour. Two cars start from cities a and B at the same time and run backward. After 2.4 hours, the two cars are 580 kilometers apart. How many kilometers are there between cities a and B?

Set a and B two places together x kilometers
Then: 2.4 (80 + 95) + x = 580
Do it yourself

The solution of the equation AX-1 = 3 (2a-x) of X is x = - 2, and the value of a is obtained
Another question: when Xiao Ming was solving the equation, he accidentally polluted a constant in the equation. He couldn't see it clearly. What should he do with the polluted equation 2x + 1 / 2 = 1 / 2x -? The solution of this equation is the same as that of equation 3x + 6 = 0

Substitute x = - 2 into the equation
-2a-1=3(2a+2)
-2a-1=6a+6
8a = -7
a=-7/8
3x + 6 = 0, the solution is x = - 2
Let the obscure number a be substituted into the original equation
-2*2+1/2=1/2*(-2)-a
a=-1+4-1/2=5/2

Two cars a and B run from ab 960 meters apart and meet after 6 hours. It is known that the speed of car a is 3 / 5 of that of car B,
What are the speeds of a and B?

Speed of vehicle B: 960 △ 6 (1 + 3 / 5) = 100 km / h
Speed of car a: 100 × 3 / 5 = 60 km / h

I can't solve the equation: 2x (7-2x) - 5x (8 + x) = 3x (5-3x) + 13,

Let's go
14x-4x^2-40x-5x^2=15x-9x^2+13
Consolidation, - 41x = 13, x = - 13 / 41

When a dog starts at 6km / s, a runs from a to B, meets B and turns back to a
Party A and Party B depart from each other at the same time with the distance of 12km. The speed of Party A is 5km / s, and that of Party B is 3km / s. a dog runs from Party A to Party B at the speed of 6km / s. when meeting Party B, it returns to Party A and turns to Party B for the distance

Encounter time: 12 / (3 + 5) = 1.5s
That is, before the meeting, Party A and Party B walked for 1.5 seconds
And the dog has been running all this time without stopping
So the distance the dog runs is
6*1.5=9km

Circular decimal 0.361817281728172 Which is the number 2009 after the decimal point?

1

The car runs 100 kilometers per hour and the bus 80 kilometers per hour
How long is the highway between the two places? (2) if two vehicles start from the gas station at the same time and go northward along the same highway, they just arrive at the destination in two hours. How long is the highway between the two places?

The car runs 100 kilometers per hour and the bus 80 kilometers per hour. (1) if two cars start from two places at the same time and travel along the same road, they will meet at the gas station two hours later. How long is the road between the two places? (100 + 80) × 2 = 360 kilometers. (2) if two cars start from the gas station at the same time and travel along the same road