सिद्ध कीजिए कि -
` ( tanA + sec A - 1)/( tan A - sec A + 1 ) = (cos A )/( 1 - sin A ) `

Explanation

` L.H.S = ( tan A + sec A - 1) /( tan A - sec A + 1) `
` = (( tan A + sec A) - sec^(2) A- tan^(2) A)/(tan A - sec A + 1 ) `
` ( tan A = secA) - ( sec A - tan A) `
` = ((secA + tan A))/(tan A - sec A + 1) `
` = ((tan A + secA)(1 - sec A + tan A))/(tan A- sec A+1)`
` = tan A + sec A`
` = (( tan A + sec A) ( sec A - tan A))/(sec A - tan A)`
` (sec^(2) A - tan^(2) A )/(1/(cosA)-(sinA)/(cosA))= 1/((1-sinA)/(cosA))`
` = (cos A)/(1- sinA) = R.H.S `