1.

Let `f(x)={{:(,3sinx+a^(2)-10a+30,x in Q),(,4 cos x,x in Q):}"which"`one of the following statements is correct?A. f(x) is continuous for all x when a=5B. f(x) must be continuous for all, x when a=5C. f(x) is continuous for all x, `=2pix-tan^(-1)((3)/(4)),n in Z,"when a=5"`D. f(x) is continuous for all `x=2pix-tan^(-1)((4)/(3)),n in Z` when a=5

Answer» Correct Answer - C
If f(x) is continuous for all x, then `3 sinx+a^(2)-10a+30=4cosx "for all x"`
`Rightarrow (a-5)^(2)+5 cos x-3sinx"for all x"`
`Rightarrow (a-5)^(2)+5 cos (x+theta),"where " theta="tan"^(-1)(3)/(4)"for all x"`
We observe that `LHS ge 5`. So, the two sides of the above equality are euqal if `a=5 and cos(x+theta)=1`
`Rightarrow a=5 and x=2pix-"tan"^(-1)(3)/(4)`


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