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without using trigonometric tables, find the value of cos70/sin20 + cos57 cosec33- 2cos60.

Here is the solution for your question,
   cos 70/sin 20+cos 57 x cosec 33 - 2cos 60
  We know that cos (90-x)= sinx
        Therefore,cos 70=cos (90-20)=sin 20
                 Similarly,cos 57=cos (90-33)=sin 33
                 
               Therefore,the equation can be simplified as
                  sin 20/sin 20 + sin 33 x 1/sin 33 - 2 cos 60      (since, cosec 33=1/sin 33)
                   1+1-2 x 1/2     (since,cos 60=1/2)
                    = 2 -1
                    =1

 Therefore, cos 70/sin 20 + cos 57 x cosec 33 - 2 cos 60 = 1
 
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In the question it is mentioned not to use the trigonometry table but you used for cos60....
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In the question it is mentioned not to use the trigonometry table but you used for cos60....
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This question is based on trigonometry then how will you solve it without using the values.Then u sit and solve the question,if u can.
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They have mentioned in the question not to use the trigonometric table, yet we substituted  cos 60=1/2
I don't understand what this means..

 
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