由題意得：(4cosα - 3sinα)(2cosα - 3sinα) = 0
解得 tanα = 4/3 或 tanα = 2/3。
因 α ∈ (π/4, π/2)，tanα > 1，故 tanα = 4/3。
(1) tan(a + π/4) = (tanα + 1)/(1 - tanα) = (4/3 + 1)/(1 - 4/3) = -7
答：tan(a + π/4) = -7
解得 tanα = 4/3 或 tanα = 2/3。
因 α ∈ (π/4, π/2)，tanα > 1，故 tanα = 4/3。
(1) tan(a + π/4) = (tanα + 1)/(1 - tanα) = (4/3 + 1)/(1 - 4/3) = -7
答：tan(a + π/4) = -7