CBSE Class 10 Answered

if cosec∅+cot∅=k then show that cos∅k²-1/k²+1

Asked by rc1827805 | 23 Dec, 2022, 08:11: PM

Expert Answer

begin mathsize 14px style cos e c space theta space plus space c o t space theta space equals space k end style

begin mathsize 14px style fraction numerator 1 over denominator sin space theta end fraction plus space fraction numerator cos space theta over denominator sin space theta end fraction space equals space k end style

begin mathsize 14px style fraction numerator 1 space plus space cos space theta over denominator sin space theta end fraction space equals space k end style

...........................(1)

If we multiply numerator and denominator by ( 1 - cosθ ) , then we get

begin mathsize 14px style fraction numerator sin space theta over denominator 1 space minus space cos space theta end fraction equals space space k end style

..................................(2)

If we multiply eqn.(1) and eqn.(2) , then we get

begin mathsize 14px style fraction numerator 1 space plus space cos space theta over denominator 1 space minus space cos space theta end fraction space equals space k squared end style

If we subtract 1 from LHS and RHS , we get after simplification

begin mathsize 14px style fraction numerator 2 space cos space theta over denominator 1 space minus space cos space theta end fraction space equals space k squared space minus space 1 end style

............................(3)

If we add 1 to LHS and RHS , we get

begin mathsize 14px style fraction numerator 2 space over denominator 1 space minus space cos space theta end fraction space equals space k squared space plus space 1 end style

............................(4)

By dividing eqn.(3) by eqn.(4) , we get

begin mathsize 14px style cos space theta space equals space fraction numerator k squared minus 1 over denominator k squared plus 1 end fraction end style

Answered by Thiyagarajan K | 24 Dec, 2022, 12:25: AM

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