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№1
![0,04 leq 5^{2-x} leq 25 \ 5^{-2} leq 5^{2-x} leq 5^2 \ -2 leq 2-x leq 2 \ -4 leq -x leq 0 \ 0 leq x leq 4 \ OTBET:0; 1; 2; 3; 4. 0,04 leq 5^{2-x} leq 25 \ 5^{-2} leq 5^{2-x} leq 5^2 \ -2 leq 2-x leq 2 \ -4 leq -x leq 0 \ 0 leq x leq 4 \ OTBET:0; 1; 2; 3; 4.](https://tex.z-dn.net/?f=0%2C04+leq+5%5E%7B2-x%7D+leq+25+%5C++5%5E%7B-2%7D+leq+5%5E%7B2-x%7D+leq+5%5E2++%5C+-2+leq+2-x+leq+2+%5C+-4+leq+-x+leq+0+%5C+0+leq+x+leq+4+%5C+OTBET%3A0%3B+1%3B+2%3B+3%3B+4.)
№3
![frac{sina}{1+cosa} + frac{1+cosa}{sina} = frac{2}{sina} \ frac{sin^2a+(1+cosa)^2}{sina(1+cosa)} = frac{2}{sina} \ frac{sin^2a+1+2cosa+cos^2a}{sina(1+cosa)}= frac{2}{sina} \ frac{2+2cosa}{sina(1+cosa)}= frac{2}{sina} \ frac{2(1+cosa)}{sina(1+cosa)} = frac{2}{sina} \ frac{2}{sina} = frac{2}{sina} frac{sina}{1+cosa} + frac{1+cosa}{sina} = frac{2}{sina} \ frac{sin^2a+(1+cosa)^2}{sina(1+cosa)} = frac{2}{sina} \ frac{sin^2a+1+2cosa+cos^2a}{sina(1+cosa)}= frac{2}{sina} \ frac{2+2cosa}{sina(1+cosa)}= frac{2}{sina} \ frac{2(1+cosa)}{sina(1+cosa)} = frac{2}{sina} \ frac{2}{sina} = frac{2}{sina}](https://tex.z-dn.net/?f=+frac%7Bsina%7D%7B1%2Bcosa%7D+%2B+frac%7B1%2Bcosa%7D%7Bsina%7D+%3D+frac%7B2%7D%7Bsina%7D++%5C++frac%7Bsin%5E2a%2B%281%2Bcosa%29%5E2%7D%7Bsina%281%2Bcosa%29%7D+%3D+frac%7B2%7D%7Bsina%7D++%5C++frac%7Bsin%5E2a%2B1%2B2cosa%2Bcos%5E2a%7D%7Bsina%281%2Bcosa%29%7D%3D+frac%7B2%7D%7Bsina%7D+++%5C++frac%7B2%2B2cosa%7D%7Bsina%281%2Bcosa%29%7D%3D+frac%7B2%7D%7Bsina%7D+++%5C++frac%7B2%281%2Bcosa%29%7D%7Bsina%281%2Bcosa%29%7D+%3D+frac%7B2%7D%7Bsina%7D++%5C++frac%7B2%7D%7Bsina%7D+%3D+frac%7B2%7D%7Bsina%7D+)
№3
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