![{cos}^{2} a = 1 - {sin}^{2} a = 1 - (\frac{3 \sqrt{11} }{10} )^{2} = 1 - \frac{99}{100} = \frac{1}{100} \\ cosa = + - \frac{1}{10}](https://tex.z-dn.net/?f=+%7Bcos%7D%5E%7B2%7D+a+%3D+1+-++%7Bsin%7D%5E%7B2%7D+a+%3D+++1+-++%28%5Cfrac%7B3+%5Csqrt%7B11%7D+%7D%7B10%7D+%29%5E%7B2%7D++%3D+1+-++%5Cfrac%7B99%7D%7B100%7D++%3D++%5Cfrac%7B1%7D%7B100%7D++%5C%5C+cosa+%3D++%2B++-++%5Cfrac%7B1%7D%7B10%7D+)
Но т.к. pi/2 < a < pi, где cosa < 0, то cosa = -1/10
1) 16 + 33 + 14 + 37 = (16 + 14) + (33 + 37) = 30 + 70 = 100
2) 25 * 14 * 4 * 5 = (25 * 4) * (14 * 5) = 100 * 70 = 7000
3) 3/5 + 3 3/4 + 1 2/5 + 1 1/4 = (3/5 + 1 2/5) + (3 3/4 + 1 1/4) = 2 + 5 = 7
4) 3,2 * 5/6 * 5 * 6 = (3,2 * 5) * (5/6 * 6) = 16 * 5 = 80
5) 4,7 - 2,13 + 5,3 - 2,87 = (4,7 + 5,3) + (- 2,13 - 2,87) = 10 - 5 = 5
6) 2 1/4 * 1 1/7 * 4 * 7 = (2 1/4 * 4) * (1 1/7 * 7) = (9/4 * 4) * (8/7 * 7) = 9 * 8 = 72
7) 3,81 * 4,3 + 6,19 * 4,3 = 4,3 * (3,81 + 6,19) = 4,3 * 10 = 43
8) (4 - 3/10 - 1/5) * 10 = (4 - 3/10 - 2/10) * 10 = 40 - 3 - 2 = 35
3*48=8*18верное
6*9=1*54верное
1*42=6*7верное
5*72=18*20не верное
100*12=240*5верное
4*25=5*16не верное
3*44=4*33верное
42*7=49*6верное