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Find the range of the following functions given by f(x) = 1 + 3 cos2x (Hint: –1 ≤ cos 2x ≤ 1 ⇒ –3 ≤ 3 cos 2x ≤ 3 ⇒ –2 ≤ 1 + 3cos 2x ≤ 4) - Mathematics

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प्रश्न

Find the range of the following functions given by f(x) = 1 + 3 cos2x

(Hint: –1 ≤ cos 2x ≤ 1 ⇒ –3 ≤ 3 cos 2x ≤ 3 ⇒ –2 ≤ 1 + 3cos 2x ≤ 4)

योग

उत्तर

We know the value of cos 2x lies between –1, 1

So –1 ≤ cos 2x ≤ 1

Multiplying by 3, we get

–3 ≤ 3cos 2x ≤ 3

Adding 1, we get

–2 ≤ 1 + 3cos 2x≤ 4

Or, –2 ≤ f(x) ≤ 4

Hence f(x) ∈ [–2, 4]

Therefore, the range of f = [–2, 4]

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अध्याय 2: Relations and Functions - Exercise [पृष्ठ २९]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 2 Relations and Functions
Exercise | Q 18.(iv) | पृष्ठ २९

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