Question

if costheta - sintheta =acube and sectheta - costheta= bcube, then a*2b*2(a*2+b*2) =​

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Secondary School 

 

Math 

 

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If cosec theta - sin theta = a3 and sec theta - cos theta = b3 prove that a2b2 ( a2+ b2) = 1

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 by Alewilsharij 26.08.2016

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Golda 

 

Ace

Consider cosec theta - sin theta = a³

⇒ !/sin theta - sin theta = a³

⇒ 1 - sin² theta/sin theta = a³

cos² theta/ sin theta = a³ → (1)

⇒ (cos² theta/sin theta)²/³ = (a³)²/³

⇒ cos⁴/³ theta/sin²/³ theta = a² → (2)

Now consider, sec theta - cos theta = b³

⇒ 1/cos theta - cos theta = b³

⇒ 1 - cos²theta/cos theta = b³

⇒ sin² theta/cos theta = b³ → (3)

⇒ (sin² theta/cos theta)²/³ = (b³)²/³

⇒ sin⁴/³ theta/cos²/³ theta = b² → (4)

Multiply (2) and (4), we get

(cos⁴/³ theta/sin²/³ theta)× (sin⁴/³ theta/cos²/³ theta) = a²b² → (5)

a² + b² =(cos⁴/³ theta/sin²/³ theta) + (sin⁴/³ theta/cos²/³ theta)

(cos² theta + sin² theta)/(sin²/³ theta cos²/³ theta)

= 1/sin²/³ theta cos²/³ theta

Consider, a²b²(a²+b²) = (sin²/³ theta cos²/³ theta) × 1/sin²/³ theta cos²/³ theta

= 1 Hence proved.