Q20 of 113 Page 547

Prove that

(i)


(ii)


(iii)


(i)

………[Using –2sinx.siny = cos(x + y)–cos (x–y)]




(ii)


………..[using 2cosx.cosy = cos(x + y) + cos(x–y)]




(iii)


...[Using2sinx.cosy = sin(x + y) + sin(x–y)]




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18

If , where , find the values of

(i) sin (x + y)


(ii) cos (x – y)


(iii) tan (x + y)


 19

Prove that

(i)


(ii)


(iii)


(iv)


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 2

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