बिना त्रिकोणमितीय सारिणी के प्रयोग के निम्नलिखित को सिद्ध करे
`(i) sin40^(@)*sin50^(@)-cos40^(@)*cos50^(@)=0`
`(ii) (sin36^(@)+cos54^(@))(sin36^(@)-cos54^(@))=0`
`(iii) sin25^(@)+cos65^(@)=2sin25^(@)=2cos65^(@)`
`(iv)cos^(2)75^(@)+cos^(2)15^(@)=1`
`(v) sec50^(@)*sin40^(@)+cos40^(@)cosec50^(@)=2`
`(vi)cosec^(2)74^(@)-tan^(2)16^(@)=1`
`(vii) (2sin67^(@))/(cos23^(@))-(tan40^(@))/(cot50^(@))-cos0^(@)=0`
`(viii) sin48^(@)*sec42^(@)+cos48^(@)*cosec42^(@)=2`
`(ix) ((sin35^(@))/(cos55^(@)))^(2)+((cos55^(@))/(sin35^(@)))^(2)-2cos60^(@)=1`
`(x) (sin70^(@))/(cos20^(@))+(cosec20^(@))/(sec70^(@))-2cos70^(@)cosec20^(@)=0`