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प्रश्न
Prove that cosec θ – cot θ = `sin theta/(1 + cos theta)`
उत्तर
L.H.S = cosec θ – cot θ
= `1/sintheta - costheta/sintheta`
= `(1 -costheta)/sintheta`
= `(1 - costheta)/sintheta xx (1 + costheta)/(1 +costheta)` .....[On rationalising the numerator]
= `(1 - cos^2theta)/(sintheta(1 +costheta))`
= `(sin^2theta)/(sintheta(1 + costheta))` .....`[(because sin^2theta + cos^2theta = 1),(therefore 1 - cos^2theta = sin^2theta)]`
= `sintheta/(1 + costheta)`
= R.H.S
∴ cosec θ – cot θ = `sin theta/(1 + cos theta)`
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Activity:
L.H.S = `square`
= `square/sintheta + sintheta/costheta`
= `(cos^2theta + sin^2theta)/square`
= `1/(sintheta*costheta)` ......`[cos^2theta + sin^2theta = square]`
= `1/sintheta xx 1/square`
= `square`
= R.H.S
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`square/square` = cosec2θ ......[Taking root on the both side]
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