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प्रश्न
sin4A – cos4A = 1 – 2cos2A हे सिद्ध करा.
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उत्तर
डावी बाजू = sin4A – cos4A
= (sin2A)2 – (cos2A)2
= (sin2A + cos2A)(sin2A – cos2A) .....[∵ a2 – b2 = (a + b)(a – b)]
= (1)(sin2A – cos2A) ......[∵ sin2A + cos2A = 1]
= sin2A – cos2A
= (1 – cos2A) – cos2A ......`[(because sin^2"A" + cos^2"A" = 1),(therefore 1 - cos^2"" = sin^2"A")]`
= 1 – 2cos2A
= उजवी बाजू
∴ sin4A – cos4A = 1 – 2cos2A
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संबंधित प्रश्न
sec4θ - cos4θ = 1 - 2cos2θ
`tanA/(1 + tan^2A)^2 + cotA/(1 + cot^2A)^2` = sin A cos A
sec2θ + cosec2θ = sec2θ × cosec2θ
cosec θ.`sqrt(1 - cos^2theta) = 1` हे सिद्ध करा.
sec2θ − cos2θ = tan2θ + sin2θ हे सिद्ध करा.
tan2θ – sin2θ = tan2θ × sin2θ हे सिद्ध करण्यासाठी खालील कृती पूर्ण करा.
कृती: डावी बाजू = `square`
= `square (1 - (sin^2theta)/(tan^2theta))`
= `tan^2theta (1 - square/((sin^2theta)/(cos^2theta)))`
= `tan^2theta (1 - (sin^2theta)/1 xx (cos^2theta)/square)`
= `tan^2theta (1 - square)`
= `tan^2theta xx square` .....[1 – cos2θ = sin2θ]
= उजवी बाजू
cot2θ – tan2θ = cosec2θ – sec2θ हे सिद्ध करा.
`(sintheta + "cosec" theta)/sin theta` = 2 + cot2θ हे सिद्ध करा.
sin θ (1 – tan θ) – cos θ (1 – cot θ) = cosec θ – sec θ हे सिद्ध करा.
जर cos A + cos2A = 1, तर sin2A + sin4A = ?
