4a^2-20a+25+20a-5a^2=-a^2+25
(-2/5)^2+25=4/25+25=25целых4/25
(cos²a-sin²a) /(cosa+sina)-cosa=(cosa-sina)*(cosa+sina) / (cosa+sina)-cosa=cosa-sina-cosa=-sina
1) pi/2 < a < pi, поэтому sin a > 0, cos a < 0
cos a = -√6/4; cos^2 a = 6/16
sin^2 a = 1 - cos^2 a = 1 - 6/16 = 10/16; sin a = √10/4
tg a = sin a / cos a = (√10/4) : (-√6/4) = -√10/√6 = -√5/√3 = -√15/3
2) 0 < a < pi/2, поэтому sin a > 0, cos a > 0
sin a = √2/3; sin^2 a = 2/9
cos^2 a = 1 - sin^2 a = 1 - 2/9 = 7/9; cos a = √7/3
tg a = sin a / cos a = (√2/3) : (√7/3) = √2/√7 = √14/7
3) 3pi/2 < a < 2pi, поэтому sin a < 0, cos a > 0
cos a = 15/17; cos^2 a = 225/289
sin^2 a = 1 - cos^2 a = 1 - 225/289 = 64/289; sin a = -8/17
tg a = sin a / cos a = (-8/17) : (15/17) = -8/15
<span>№2
1) (4,5-11,7)/(1,9+1,7) = -7.2/ 3.6= -2</span><span>
2) 139/4+(27,3*1/3-4,1):1/2-5/4</span> = 34.75 + 5/ 0.5 - 1.25= 34.75 +10 _1.25= 43.5 <span>
3) 441*362+441^2-441*303= </span>159 642+194 481-133 623=220 500
№3
<span>1) -m+2n
Если m=9,n=-6</span> , то -9+2*(-6)=-9-12=-21
<span>2)-3n^2-m^3
Если m=-4,n=5 , то-3*5^2-(-4)^</span>3=-75+64=-11
<span>3) m-n(m+n)
Если m=-3/5,n=-0.2 , то -(3/5)-(-0.2)*(-(3/5)+(-0.2))=-0.6+0.2*(-0.6-0.2)=
=-0.6-0.16=-0.76</span>
№4
<span>1)1.2(4y-3)-3(12+5y)= 4.8у-3.6-36-15у=-10.2у-39.6</span><span>
2)-5(3a-1)+(6-4a)2-3(2+a)=-15а+5+12-8а-6+3а=-20а-11
-20а=11 | : (-20)
а=-0.55
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