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7 years, 2 months ago
if sin^8 θ + cos^8 θ - 1 = 0, then what is the value of cos^2 θ sin^2 θ (if θ ≠ 0 or π/2)?
6 years, 4 months ago
Given: sin8θ+cos8θ=1
Dividing by 2–√on both sides,12√sin8θ+12√cos8θ=12√—(1)
Since, sin45=cos45=12√
LHSof (1)=>cos45sin8θ+sin45cos8θ—(2)
RHSof (1)=12√=sin45
Since sin(A+B)=sinAcosB+cosAsinB,
(2)=>sin(45+8θ)=12√=sin45=sin135
Considering RHS=sin45
=>45+8θ=45=>8θ=0=>θ=0, but θ is not 0 (given)
Considering RHS=sin135
=>45+8θ=135=>8θ=90=>θ=908=454—(3)
Requested answer is cos2θ∗sin2θ=(cosθ∗sinθ)2=([2∗cosθ∗sinθ]2)2—(4)
Since 2sinθcosθ=sin2θ,(4) can be written as (sin2θ)24=(sin(2∗454))24
=(sin45/2)^2/4------->(5)
sin(45/2)=0.3827,(5) can be evaluated to 0.036612
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