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Relations And Functions

Question
CBSEENMA12035650

Prove space that space straight y equals fraction numerator 4 space sin space straight theta over denominator 2 space plus cos space straight theta end fraction space minus straight theta space is space an space increasing space function space of space straight theta space on space open square brackets 0 comma straight pi over 2 close square brackets

Solution
considering space the space equation
straight y space equals fraction numerator 4 space sin space straight theta over denominator 2 space plus cos space straight theta end fraction minus straight theta space

differentiation space straight y space straight w. straight r. straight t space straight theta

dy over dθ space equals space space fraction numerator left parenthesis 2 space plus cos space straight theta right parenthesis space plus space 4 space sin squared space straight theta over denominator left parenthesis 2 space plus space cos space straight theta right parenthesis squared end fraction space space minus space 1

equals space space fraction numerator 8 space cos space space plus 4 space cos squared space space plus 4 space sin squared space straight theta over denominator left parenthesis 2 space plus cos space straight theta right parenthesis squared end fraction space space minus space 1

space equals space fraction numerator 8 space cos space space plus 4 over denominator left parenthesis 2 space plus cos space straight theta space right parenthesis squared end fraction minus 1

equals space fraction numerator 4 space cos space space minus space cos squared space straight theta over denominator left parenthesis 2 space plus space cos space straight theta right parenthesis squared end fraction

dy over dθ space space equals space fraction numerator cos space space left parenthesis space 4 minus space cos space straight theta space right parenthesis over denominator left parenthesis 2 plus cos space straight theta right parenthesis squared end fraction

for space increasing space dy over dθ space greater than space 0 space comma space straight theta space element of space open parentheses 0 comma space straight pi over 2 close parentheses

0 space less than for minus of space cos space straight theta space less than for minus of space space 1

left parenthesis 2 plus space cos space straight theta right parenthesis squared space always space greater space than space 0

so space comma space dy over dθ space is space increasing space on open square brackets 0 comma straight pi over 2 close square brackets