If 5 / 2 π

∵ （5 / 2）π < a < （11 / 4）π∴ 5 π < 2a < （11 / 2）π∵ sin 2a = - 4 / 5 ∴ cos 2a = - 3 / 5∴ cos ² a - sin ² a = - 3 / 5（cos ² a - sin ² a）/ （sin ² a + cos ² ...

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1. If Tana = 1 / 3, then the value of 2cos square a + sin2a? I want to simplify the method before calculating
2. In the triangle ABC, if 5 (b square + C square - a square) = 6BC, find sin2a + 2sina square / 1 + Tana Please~~
3. The process of finding 1 / (sin2a) with Tana = 2 is known
4. The vertex A.D.C of square oabc rectangle ADEF on the coordinate axis point F on AB point b.e area of ad = 0.5adef on graph with function y = 1 / X (x > 0)
5. If the vertex B of the square oabc and the vertex e of the square ADEF are both on the image of the function y = 1 / X (x > 0), what are the coordinates of the point e
6. As shown in the figure, in the parallelogram oabc, it is known that the coordinates of O and a are o (0,0) a (5 radicals 3,0), and the angle AOC is 60 degrees AB = 2 root sign 3, the distance from C point to X axis is 3 (1) Finding the coordinates of B and C (2) Finding the area of parallelogram oabc (3) Translate the parallelogram to the right by three root signs and three unit lengths, and get the four vertex coordinates of the parallelogram
7. As shown in the figure, in the parallelogram ABCO, it is known that the coordinates of two points a and C are a (root 3, root 3) respectively Title: 1. Find the coordinates of point B 2. Translate the parallelogram oabc to the left by 3 unit lengths of the root, and get the coordinates of the four vertices of the parallelogram 3. Find the area of parallelogram oabc (it's not necessary to solve the root sign with the knowledge of grade one in junior high school. Thank you. Hurry up ~ ~~~~~~~~~~~~~~~~~
8. As shown in the figure, the coordinates of a, B and C are (3,0), (1, root 3), (0,1) respectively, so as to find the area of the quadrilateral oabc
9. As shown in the figure, in the parallelogram ABCO, the coordinates of C and D are C (- 3 radical 3,0), B (- 3 radical 3. - 3 radical), and (1) find the coordinates of point a As shown in the figure, in the parallelogram ABCD, the coordinates of C and D are C (- 3 radical 3,0), B (- 3 radical 3. - 3 radical), (1) find the coordinates of point a (2) The parallelogram aboc is translated to the right by two root signs and three unit lengths, and the coordinates of four vertices of the parallelogram a'b'o'c 'are obtained (3) Finding the area of a parallelogram aboc There's no mistake. It's the coordinates of A
10. Quadratic function y = xsquare - 4x + 1, find the function analytic formula of the image about the Y axis, the image analytic formula of the X axis, and the image analytic formula of the origin centrosymmetry
11. It is known that Tana = 3 / 4,0
12. tana=3/4 sin2a= If a is the fourth quadrant angle, Tana = 3 / 4, then sin2a=
13. (1 + Tana) / (1-tana) = 3 + 2 √ 2, find sin2a
14. Given xy = 35, find the value of x2 − XY + 2y2x2 + 2XY − Y2
15. If | x + Y-2 | + [2xy-1] 2 [this 2 is square] = 0, find the value of x2 + 6xy + Y2
16. Given 3x2 + 2Y2 = 2x, find the maximum value of x2 + Y2
17. Given 3x2 + 2Y2 = 9x, find the maximum value of x2 + Y2 3x2 means 3x square, and so on Urgent, Can we use the monotonicity and the maximum (minimum) value of the function of higher one to answer?
18. If x2 + y2 = 1, find the maximum and minimum of y = 3x2 + 4y2-2x-5 Specific steps should be taken
19. If x and y satisfy x2 + y2 = 1, then the minimum value of (Y-2) / (x-1) is; the maximum value of X / 3 + Y / 4 is I don't understand why (Y-2) / (x-1) can be regarded as the slope of the line between any point (x, y) and point (1,2) on a circle
20. -Is x2 + 2xy-y2 a complete square If it can be used, does it mean it can be used? that. 4Y & # 178 / / X & # 178; - XY + Y & # 178; this should not work, right?