Question

if tan a=17/18 tan b = 1/35 then cos (a+b)=​

Answer 1

Answer

cos(a+b) =  1/√2

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tan (a+b)  =tan a+tan b/(1-tan a*tan b)

=(17/18 +1/35) /  (1-17*1/18*35)

=(17*35+1*18)/630 /(630-17)/630

= (595+18)/630 / 613/630

=613/630  /  613/630

=1

Thus a+b=45°

cos(a+b)= cos 45° =1/√2

Answer 2

Answer:

cos (a+b)= cos 45° = 1 /√2

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