Maths-
General
Easy

Question

The value of k, for which left parenthesis cos invisible function application x plus sin invisible function application x right parenthesis to the power of 2 end exponent plus k sin invisible function application x cos invisible function application x minus 1 equals 0 is an identity, is

  1. –1    
  2. –2    
  3. 0    
  4. 1    

The correct answer is: –2


    Given, left parenthesis cos invisible function application x plus sin invisible function application x right parenthesis to the power of 2 end exponent plus k sin invisible function application x cos invisible function application x minus 1 equals 0 comma for all x
    Þ cos to the power of 2 end exponent invisible function application x plus sin to the power of 2 end exponent invisible function application x plus 2 cos invisible function application x sin invisible function application x plus k sin invisible function application x cos invisible function application x minus 1 equals 0 comma for all x
    Þ left parenthesis k plus 2 right parenthesis cos invisible function application x sin invisible function application x equals 0 comma for all x Þ k plus 2 equals 0 Þ k equals negative 2

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