<u> 2 </u> <u>1+х</u>
(х-3)2 х2-9
<u> 2 </u> <u>1+х</u>
(х-3)(х-3) (х-3)(х+3)
общ знаменатель (х-3)(х-3)(х+3)
<u>sin 50 = cos 40</u>
sin 50 · cos 20 · (1 - tg 40 ·tg 20) =
= cos 40 · cos 20 · (1 - tg 40 ·tg 20) =
= cos 40 · cos 20 · (1 - (sin40 · sin20)/(cos 40 ·cos 20)) =
= cos 40 · cos 20 · (cos 40 ·cos 20 - sin40 · sin20)/(cos 40 ·cos 20) =
= cos 40 ·cos 20 - sin40 · sin20 =
= cos (40 + 20) =
= cos 60 = 0.5
A = (t+1)^(2/3) => a^3 = (t+1)^2
b = (t-1)^(2/3) => b^3 = (t-1)^2
b^3 = (t-1)^2 = (<u>t+1</u>-1 - 1)^2 = ((t+1) - 2)^2 = (t+1)^2 - 4(t+1) + 4 =
= a^3 -4*a^(3/2) + 4
только знак второго слагаемого меня слегка смущает, т.к. (t+1) = +-корень(a^3)