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   * Sin approximation Between 1 to 34(degree)

   1.Sin(30)=0.5

       Sin (30)

       Step 1:Take the Angle that you are looking for.

       Step 2:Here we have 30 degree, label as X         (30=X)

                  Use this formula,

                  Sin (X)=  X/60

                       or

                 (5X/3) and then divide that answer by 100.

       Step 3:

             Sin 30=(30/60)

                       =0.5

Now,

        Sin (25)

        = (25/60)

        =0.42

       Sin (20)

       =(20/60)

       =0.33

 * Some quick Calculation

 

      (36)2 = 1296

      Using algebra we can calculate little bit fast:

        (35+1)2   

      = (35)2+2(35)(1)+(1)2

      = (1225)+(70)+(1)

     =1296

    (48)2

    =(50-2)2

    =(50)2-2(50)(2)+(2)2

     =(2500)-200+4

    =2304

   (67)2

   =(70-3)2

   =(70)2-3(70)(3)+(3)2

   =4900-420+9

   =4489

        11*99 =1089

        To calculate use this short cut method:

        11*99

        Step 1: subtract 1 from the number besides 99

                    11-1=10

       Step 2: Then subtract number besides 99 from the 100.

                  100-11=89

       Step 3: Combine Step 1 and Step 2:

                   1089

      58*99

      58-1=57

      100-58=42

      Answer: 5742

      87*99

      87-1=86

      100-87=13

      Answer: 8713

 

        325*5=1625

        495*5=2475

        To calculate use this short cut method:

        Step 1: Separate the digits from the last digit 5.

                   325= 32(separated)       5

                   495= 49(Separated)      5     

       Step 2: If the separated number is even(32), simply divide by 2.(32/2)=16

                  32/2 =16

                  If the separated number is odd(49), subtract 1 from separated number(49-1)=48

                  and then divide by 2. (48/2)=24

       Step 3: If the separated number is even, just put "25" after divided number.

                  1625

                 If the separated number is odd, just put "75" after divided number.

                 2475

      745*5

     74 is even

     (74/2)=37

     Put 25(Because 74 is "Even") after 37

     Answer: 3725

    655*5

    65 is odd

    (65-1)/2=32

    Put 75(Because 65 is "Odd") after32

    Answer:3275

   15745*5

   1574 is even

   (1574)/2=787

   Since 1574 is "Even"

   Answer is 78725

   17855*5

   1785 is odd

   (1785-1)=1784 then (1784/2)=892

  Since 1785 is "Odd"

  Answer is 89275.

 

  * Exercise

  #1

           Sin 12

          Sin 04

          Sin 29

          Sin 18

         Sin 33

 #2

          (28)2

          (74)2

          (98)2

          (47)2

         (39)2

 #3

           525*5

           4301*5

           688*5

           225*5

          1085*5

   * Check the Answer in your calculator.

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