cos172^\circ \\\\b>a>d>c" alt="5)\; \; a=sin3\; ,\; b=sin2\; ,\; c=cos3\; ,\; d=cos4\\\\a\approx sin172^\circ \ \textgreater \ 0\; ,\; b\approx sin115^\circ \ \textgreater \ 0\; ,\; c\approx cos172^\circ \ \textless \ 0\; ,\; d\approx cos229^\circ \ \textless \ 0\\\\sin115^\circ \ \textgreater \ sin172^\circ\; ,\; \; \; cos172^\circ \ \textless \ cos229^\circ \\\\cos172^\circ =cos(90^\circ +72^\circ )=-sin72^\circ \\\\cos229^\circ =cos(90^\circ +139^\circ )=-sin139^\circ =-sin(180^\circ -41^\circ )=-sin41^\circ \\\\sin115^\circ \ \textgreater \ sin172^\circ \ \textgreater \ -sin41^\circ \ \textgreater \ -sin72^\circ \; \; \; \Rightarrow \\\\sin115^\circ \ \textgreater \ sin172^\circ \ \textgreater \ cos229^\circ >cos172^\circ \\\\b>a>d>c" align="absmiddle" class="latex-formula">