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Questions  

Let f(x)=x22(sin3sin2)x(cos3cos2) then

a
f(x) is positive ∀x∈R
b
f(x) assumes both positive and negative values
c
f(x) = 0 has no real roots
d
y = f(x) touches the line y = 0

detailed solution

Correct option is A

We havef(x)=x2−2(sin⁡3−sin⁡2)x−(cos⁡3−cos⁡2)∴ D=4[(sin⁡3−sin⁡2)+(cos⁡3−cos⁡2)]=82sin⁡3−22cos⁡π4+2+32As sin⁡3−22>0 and π2<2+32<π∴ D1<0Hence, f(x) > 0 ∀x∈R.

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