1. Given that cos (π / 3 + α) = - 3 / 5, sin (2 π / 3 - β) = 3 / 15, and 0 ＜α＜π / 2 ＜β＜π, the value of COS (β - α) can be obtained 2. Given sin α + sin β + sin γ = 0, cos α + cos β + cos γ = 0, the value of COS (β - γ) can be obtained There is no connection between the above two questions. You can answer one of them!

1. Given that cos (π / 3 + α) = - 3 / 5, sin (2 π / 3 - β) = 3 / 15, and 0 ＜α＜π / 2 ＜β＜π, the value of COS (β - α) can be obtained 2. Given sin α + sin β + sin γ = 0, cos α + cos β + cos γ = 0, the value of COS (β - γ) can be obtained There is no connection between the above two questions. You can answer one of them!

1、β-α=-[(π/3+α)+(2π/3-β)]
The size of π / 3 + α, 2 π / 3 - β can be analyzed from 0 ＜α＜π / 2 ＜β＜π
π / 3 + α 0 is obtained
Sin (2 π / 3 - β) > 0, so 0

When a equals (), 6a equals 2

6a=2
a=1/3
When a equals (1 / 3), 6a equals 2

Let f (x) = a ^ x + B (a > 0) (a is not equal to 1) g (x) = 2x ^ 2-5x-k. Let f (x) pass through points (1,7)
(1) Find the value of A.B
(2) When the two zeros of G (x) are respectively within (0,1) and (1,2), the value range of the real number k is obtained
(3) Let H (x) = f (x) x > 0, H = g (x) = g (x) X

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