State when f(x) is increasing , decreasing , concave up , concave down .

f(x) = sec x. tan x

⇔ f(x) = 1/cosx . cosx/sinx

⇔ f(x) = sin x

+) when f(x) is increasing => sin x increases

=> x will increase

+) f(x) is decreasing => x will decrease

+) f(x) is concave up => x ∈ (-pi/2; 0)

+) f(x) concave down => x ∈ (0; pi/2)

Step-by-step explanation:

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