Question

Prove it pleeease 25 points!!!!! Wrong answer will be reported please

Answer 1

Given cos5θ=0

cos4θcosθ−sin4θsinθ=0

(2cos  

2

2θ−1)cosθ−2sin2θcos2θsinθ=0

cosθ[2cos  

2

2θ−1−4sin  

2

θcos2θ]=0

cosθ[4cos  

2

2θ−2cos2θ−1]=0

⇒cosθ=0 or 4cos  

2

2θ−2cos2θ−1=0

⇒cosθ=0 or cos2θ=  

4

1±  

5

​  

 

​  

 

⇒cos  

2

θ=  

8

5±  

5

​  

 

​  

 

⇒(8cos  

2

θ−5)  

2

=5

⇒64cos  

4

θ−80cos  

2

θ+20=0

⇒64cos  

4

θ−80cos  

2

θ+1625=1605

Answer 2

Step-by-step explanation:

$<font color =purple><marquee>$ The correct answer is 6 Thetha.......

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