find local max then find range abs (sinx)+abs(cosx)
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Local maximum of sin x + ∣ cos x ∣ is obtained as sin x + cos x = 2 sin ( x + 4 π ) in the range, for example, [ 0 , π ] ∪ [ 2 π , 3 π ] ∪ . . . ∪ [ 2 n π , ( 2 n + 1 ) π ] ∪ . . . . The maximum value is thus 2 ≈ 1 . 4 1 4 2 .
Oh, I missed the abs before sin x .
In this case, 0 ≤ ∣ sin x ∣ + ∣ cos x ∣ ≤ 2 ⟹ maximum value of the quantity is 2 and the range is [ 0 , 2 ] .