Maths-
General
Easy

Question

he equation open parentheses cos invisible function application p minus 1 close parentheses x to the power of 2 end exponent plus open parentheses cos invisible function application p close parentheses x plus sin invisible function application p equals 0 in the variable x has real roots. Then p can take any value in the interval

  1. 3  
  2. fraction numerator 8 square root of 3 over denominator 3 end fraction  
  3. 5  
  4. fraction numerator 10 square root of 3 over denominator 3 end fraction  

The correct answer is: fraction numerator 10 square root of 3 over denominator 3 end fraction


    375 blankIn triangle A B C comma blank angle A B C equals 120 degree comma blank A B equals 3 blankandblank B C equals 4. If perpendicular constructed to the side A B blankatblank A and to the side B C blankatblank C meets at D, thenblank C D is equal to
    Note that increment P C D is right angle as shown in the figure
    Nowblank tan invisible function application 30 degree equals fraction numerator x over denominator 10 end fraction

    increment P A B blankisblank 30 degree minus 60 degree minus 90 degree blanktriangle, hence in increment P A B comma blank P B equals fraction numerator 3 over denominator sin invisible function application 30 degree end fraction equals 6
    Therefore, inblank increment P C D comma blank x equals 10 tan invisible function application 30 degree equals 10 divided by square root of 3 equals open parentheses 10 square root of 3 close parentheses divided by 3
    open parentheses cos invisible function application p minus 1 close parentheses x to the power of 2 end exponent plus open parentheses cos invisible function application p close parentheses x plus sin invisible function application p equals 0
    For this equation to have real roots D greater or equal than 0
    rightwards double arrow cos to the power of 2 end exponent invisible function application p minus 4 sin invisible function application p blank open parentheses cos invisible function application p minus 1 close parentheses greater or equal than 0
    rightwards double arrow cos to the power of 2 end exponent invisible function application p minus 4 sin invisible function application p cos invisible function application p plus 4 sin to the power of 2 end exponent invisible function application p plus 4 sin invisible function application p minus 4 sin to the power of 2 end exponent invisible function application p greater or equal than 0
    rightwards double arrow open parentheses cos invisible function application p minus 2 sin invisible function application p close parentheses to the power of 2 end exponent plus 4 sin invisible function application p blank open parentheses 1 minus sin invisible function application p close parentheses greater or equal than 0
    For every real value of p, we have
    open parentheses cos invisible function application p minus 2 sin invisible function application p close parentheses to the power of 2 end exponent greater or equal than 0 and sin invisible function application p left parenthesis 1 minus sin invisible function application p right parenthesis greater or equal than 0
    therefore D greater or equal than 0 comma blank for all sin invisible function application p element of open parentheses 0 comma blank pi close parentheses

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