without using trigonometric tables,evaluate: cos 70 degree upon 3 sin 20 degree + 4(sec square 59 degree-cot square 31 degree) upon 3 - 2 by 3 sin 90 degree
cos70 / 3sin20 + 4(sec2 59 - cot2 31)/3 - 2/3sin90
= sin(90-70) / 3sin20 + 4(sec2 59 - tan2 (90-31))/3 - 2/3sin90
= sin20 / 3sin20 + 4(sec2 59 - tan2 59)/3 - 2/3sin90
= 1/3 + 4(1)/3 - 2/3*1
= 1/3 + 4/3 - 2/3
= (1+4-2) / 3
= 1
= sin(90-70) / 3sin20 + 4(sec2 59 - tan2 (90-31))/3 - 2/3sin90
= sin20 / 3sin20 + 4(sec2 59 - tan2 59)/3 - 2/3sin90
= 1/3 + 4(1)/3 - 2/3*1
= 1/3 + 4/3 - 2/3
= (1+4-2) / 3
= 1