cos3x/2×cosx/2-sin3x/2×sinx/2
The formula is: cos (a + b) = cosa * CoSb Sina * SINB
Original formula = cos (3x / 2 + X / 2) = cos2x
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- 10. It is known that the ellipse x ^ 2 / M-Y ^ 2 = 1 (M > 1) and hyperbola x ^ 2 / n-y ^ 2 = 1 (n > 0) with the same two foci F 1 and F 2, P is one of their foci, then It is known that the ellipse x ^ 2 / M-Y ^ 2 = 1 (M > 1) and hyperbola x ^ 2 / n-y ^ 2 = 1 (n > 0) with the same two foci F 1 and F 2, and P is one of their foci, then the shape of triangle pf1f 2 is
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- 12. Let f (SiNx) = cos2x, then f (1 / 3) is equal to?
- 13. Given the vector a = (SiNx, 1), B = (cosx, 1), X ∈ R. (1) when x = π 4, find the coordinates of vector a + B; (2) if the function f (x) = | a + B | 2 + m is an odd function, find the value of real number M
- 14. Given the vector a = (SiNx, 2), B = (1, - cosx), and a is perpendicular to B, find the value of TaNx and Tan (x-card / 4)
- 15. Given that the vector a = (SiNx, 2) the vector b = (|, - cosx), and the vector a is perpendicular to the vector B. 1::: find the value of TaNx 2: find the value of Tan (x-wu / 4),
- 16. Given the vector a = (1 / 2, √ 3 / 2), B = (cosx, SiNx). If a · B = 2cos [(12K π + 13 π) / 6 + x] (K ∈ z), find the value of Tan (x + 5 π / 12) Only the answer is OK
- 17. Given the vector α = (cosx, SiNx), B = (√ 2, √ 2), a · B = 8 / 5, then the value of Tan (x - π / 4) is
- 18. If x is less than or equal to 90 degrees, greater than or equal to 0 degrees, SiNx * cosx = 1 / 2, then 1 / (1 + SiNx) + 1 / (1 + cosx) =? Detailed process! I'll collect it in an hour
- 19. Find the range of function f (x) = SiNx sinxcosx + cosx, X ∈ (π / 2,3 π / 2)
- 20. (SiNx + cosx) / (SiNx cosx) = 2, then sinxcosx =?