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[mathematics of senior two] it is known that the function f (x) = ax ^ 2 - (2a + 1) x + 2 (a > 0), and the angles a and B are the two inner angles of the acute triangle ABC ①f(sinA)>f(cosB) ②f(sinA)f(sinB) ④f(cosA)
Because a triangle is an acute triangle
So C π / 2
So π / 2 > a > π / 2-B > 0
So 1 > Sina > sin (π / 2-B) = CoSb
And f (x) = ax ^ 2 - (2a + 1) x + 2 (a > 0), the axis of symmetry is x = 1 + 1 / 2A > 1
So in X
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