Jawabanmu

2014-03-25T07:42:10+07:00
A = 20
sin 20 x cos 20 = 8/25
1/sin 20  -   1/cos 20  =  2,9238044   -    1,064177772   =   1,859626628
2014-03-25T07:50:41+07:00
(cosα-sinα) = ×
(cosα-sinα)² = ×²
cos²α - 2cosα·sinα + sin²α = ײ
(cos²α + sin²α) - 2· \frac{8}{25} = ×²

1 -  \frac{16}{25} = ×²

 \frac{25 - 16 }{25} =  \frac{9}{25}  =ײ

× =  \sqrt{ \frac{9}{25} } =  \frac{3}{5}   
cosα - sinα = \frac{3}{5}

 \frac{1}{sin \alpha }  -  \frac{1}{cos \alpha } =  \frac{cos \alpha  - sin  \alpha }{cos \alpha sin \alpha } =  \frac{ \frac{3}{5} }{ \frac{8}{25} } =  \frac{3.25}{8.5} =\frac{15}{8}