4,2:2=2,1
8-2,1=5,9
(2 5/14-1 4/21)=1 (15-8)/42=1 7/42=1 1/6
4,2:1 1/6=3,6
8-3,6=4,4
Sin^2a(1+tg^2a)*ctga=(1/cos^2a)*sinacosa=sina/cosa=tga
(sin^2t-1+tg^2tcos^4t)/cos^4t=(sin^2t-1+cos^2tsin^2t)/cos^4t=(sin^2tcos^2t-cos^2t)/cos^4t=
=(sin^2t-1)/cos^2t=-cos^2t/cos^2t=-1
1) 15/19 * 19/15 = 1
4 87/91 * 1 = 4 87/91
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2) 11/14 * 14/11 = 1
1 1/7 * 1 = 1 1/7
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3) 1 4/5 * 5/9 = 9/5 * 5/9 = 1
3,14 * 1 = 3,14
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4) 3 1/7 * 7/22 = 22/7 * 7/22 = 1
4,8 * 1 = 4,8