1 + 2sin2θ cos2θ - sin4θ - cos4θ का अधिकतम मान क्या है, जहाँ 0° < θ < 90° है?

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दिया गया है:

त्रिकोणमितीय व्यंजक 1 + 2sin2θ cos2θ - sin4θ - cos4θ है जहाँ 0° < θ < 90° है।

प्रयुक्त सूत्र:

2sinθ.cosθ = sin2θ 

sin2θ + cos2θ = 1

a2 + b2 = (a + b)2 - 2ab

गणना:

हमारे पास है 1 + 2sin2θ cos2θ - sin4θ - cos4θ

⇒ 1 + 2sin2θ cos2θ - (sin4θ + cos4θ)

⇒ 1 + 2sin2θ cos2θ - [(sin2θ)2 + (cos2θ)2]

⇒ 1 + 2sin2θ cos2θ - [(sin2θ + cos2θ)2 - 2sin2θcos2θ]

⇒ 1 + 2sin2θ cos2θ - 1 + 2sin2θcos2θ

⇒ 4sin2θ cos2θ

⇒ (2sinθ.cosθ)2

⇒ (sin2θ)2

⇒ sin2

x = 90° पर sin2x का अधिकतम मान = 1 

∴ 2θ = 90° पर sin22θ का अधिकतम मान = 1

अर्थात् θ = 45° जो दिये गए शर्त को संतुष्ट करता है।

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