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If cos alpha = 3 / 5, alpha belongs to (- π, 0), then cos (π / 4-alpha)
sinα=-4/5
cos(α-β)=cosα·cosβ+sinα·sinβ=3/5-4/5=-1/5
If the trigonometric function Tan (alpha + beta) = 2 / 5 and Tan (beta Pai / 4) = 1 / 4, then the value of Tan (alpha + 2 / 5) is?
Is to find the value of Tan (alpha + Pai / 4)
Tan (alpha + Pai / 4) = Tan [(alpha + beta) - (beta Pai / 4)]
=[Tan (alpha + beta) - Tan (beta Pai / 4)] / [1 + Tan (alpha + beta) · Tan (beta Pai / 4)]
=(2/5-1/4)/(1+2/5•1/4)
=3/22.
The trigonometric function has the following formula: sin (alpha + beta) = sin alpha cos beta + cos alpha sin beta According to this formula, we can get the sin75 degree
sin75=sin(30+45)
=sin30cos45+cos30sin45
=1/2*√2/2+√3/2*√2/2
=√2/4*(1+√3)
The period of y = (3 / 2) cos (1 / 2x - π / 6) x ∈ R,
In the function y = (3 / 2) cos (1 / 2 x - π / 6), ω = 1 / 2
So the period T = 2 π / 2 = 2 π / (1 / 2) = 4 π
Let f (x) = 2cos ^ 2 (x + π / 6) - cos ^ 2x (1) find the minimum value of F (x) and the minimum positive period (2) find that a, B, C are the three internal angles of △ ABC. If CoSb = 1 / 3, f (C / 2) = - 1 / 4, and C is an obtuse angle, find Sina Change: C for acute angle
1) F (x) = 1 + cos (2x + π / 3) - (1 + cos2x) / 2 = 1 / 2-sin2x radical 3 / 2
Minimum 1 / 2-radical 3 / 2
Minimum positive period π
2) C leads to sinc = root 3 / 2
C=π/3
A=π-B-C=2π/3-arccosB
If sin (π /6-x) =1/3, then cos (2 π /3+2x)=___________
cos(2π/3+2x)
=cos[π-(π/3-2x)]
=-cos(π/3-2x)
=-cos2(π/6-x)
=-[1-2sin²(π/6-x)]
=-[1-2*(1/3)²]
=-(1-2/9)
=-7/9
Given that the partial image of the quadratic function y = - x2 + 2x + m is shown in the figure, then the solution of the univariate quadratic equation - x2 + 2x + M = 0 is___ .
According to the meaning of the question, the symmetric axis of the quadratic function y = - x2 + 2x + m is x = 1, and the intersection point with the X axis is (3,0), / / the abscissa of the other intersection point of the parabola and the X axis is 1 - (3-1) = - 1, the intersection coordinate is (- 1,0) when x = - 1 or x = 3, the function value y = 0, that is - x2 + 2x + M = 0, on the one variable quadratic equation of X -... "
If the acute angle formed by the straight line y = 2x = 3 and the positive direction of X axis is a, and the acute angle formed by the straight line y = - 3x-1 and the positive direction of X axis is B, then the relationship between a and B is () AA is greater than B BA = B Ca ∠ B D cannot be determined PS I want more ideas. Thank you. The sooner the better Oh my God. It's true that the title is wrongly written /... 8. It's only after two digits that we can contact the function... Can we talk about it shallowly
Wrong title, I think it should be a straight line y = 2x + 3!
Make images and write their sine or cosine values
For example, Sina = 0.4 root sign 5
SINB = 0.3 root number 10
The sine function is an increasing function between [0 ° and 90 °]
Just compare the size of 0.4 root 5 and 0.3 root 10
So a
For the straight line y = - 2x + 3, y = - x, y = x, y = 4x-1, which one has the largest acute angle with the X axis and which has the smallest acute angle with the X axis, Can you find out the law? Please!
Calculate the slope k = - 2 / 1 - 1 / 1 1 / 1 4 / 1, take the larger the absolute value and the smaller the acute angle
Derivation of trigonometric function relation of mutual complementary angle
In a right triangle, there are angles a, B, C, and the corresponding sides are a, B, C. if C is 90 degrees, then a and B are mutually complementary. According to the definition of trigonometric function: Sina = A / C (opposite side to oblique side) CoSb = A / C (adjacent side to oblique side) both Sina = CoSb, that is, Sina = cos (90 degrees - a), which can be generalized
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- 2. The triangle whose largest angle is an acute angle must be an acute triangle () in a triangle, at least two angles are acute angles
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- 6. As shown in the figure, we know that in ⊙ o, the diameter Mn = 10, the four vertices of square ABCD are on the radius OM, OP and ⊙ o respectively, and ᙽ POM = 45 °, then the length of AB is () A. 5 B. 4 C. 3 D. Five
- 7. 0
- 8. 0
- 9. 0
- 10. As shown in the figure, in RT △ ABC, ∠ C = 90 °, B = 30 °, BC = 4cm, with point C as the center of the circle and 2cm long as the radius as the circle, then the position relationship between ⊙ C and ab is () A. Separation B. Tangency C. Intersection D. Tangency or intersection
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- 15. +6! How to calculate, seek specific steps
- 16. Let basketball team a and team B play. There is one winning team in each game. If one team wins four games, the game ends. Assuming that the probability of a and B winning in each game is half, try to find the expectation of the number of matches If X My calculation: P (x = 6) = C (2,5) * (1 / 2) * (1 / 2) * (1 / 2) * (1 / 2) * (1 / 2) * (1 / 2) * (1 / 2) * 2 = 5 / 8), is there any error in this?
- 17. On permutation and combination algorithm From 1 to 93, take any 8 numbers to form a sequence, which should not be in descending order. That is to say, any number in the sequence should be greater than or equal to the number in front of it. How many permutations are there? For example: {1,2,3,4,5,6,7,8} {1,2,2,2,5,6,7,8} {1,2,3,4,5,6,7,93} {10,11,30,40,44,50,60,90} The above arrangements are in line with the requirements Here are a few of the arrangements that do not meet the requirements: {1,2,3,2,4,5,6,7} {10,10,10,9,10,10,10,11} The algorithm of the first floor of hachet I would like to add that I want to express this algorithm in the form of permutation and combination. For example, how many kinds of selection methods can be expressed as three out of ten elements C (10,3), and so on I don't know if I can express this algorithm only by permutation and combination. If not, I'll have to write a cycle. In addition, I just forgot to say that if the answer given above is 1x8x6x0x8x7x8x9x4x3x00 (because continuous numbers are recognized by the system as phone numbers, they are separated by x)~
- 18. 0
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- 20. The sign rule of rational number multiplication 1. Calculate the following formula, and find out the sign rule of product? By multiplying several unequal zero numbers, the product is signed by________ The number of factors determines that when there are odd negative factors, the product is________ When there are even negative factors, the product is________ .