If sin alpha = 1/2 then the value of 3 cos alpha – 4 cos³ alpha is
Answer :
since sin alpha is = 1/2
sin 30 = 1/2
so,
alpha = 30
now,
3 cos30 – 4 cos³ 30
=> 3(√3)/2 – 4(√3/2)³
=> 3 x √3/2 – 4(3 x √3)/8
=> 12 x √3/8 – 12 x √3/8 [taking common denominator]
=> 0
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