1) Тангенс меньшего угла равен 5/12
2) Гипотенуза 13
2(n-1)! / (n-3)! - n = 8
n! = 1*2*3*...*n
n>=3 n∈N
2 * 1*2*3*...*(n-3)*(n-2)*(n-1) / 1*2*3*....*(n-3) - n = 8
2*(n-2)(n-1) - n - 8 = 0
2(n² - 2n - n + 2) - n - 8 = 0
2n² - 6n + 4 - n - 8 = 0
2n² -7n - 4 = 0
D=49 + 4*4*2 = 81
n12= (7 +- 9)/4 = - 1/2 4
n = 4
Проверка 2*3!/1! - 4 = 2*6 - 4 = 8
A1-a1q=8⇒a1(1-q)=8⇒a1=8/(1-q)
a1q+a1q²=12⇒a1(q+q²)=12⇒a1=12/(q+q²)
8/(1-q)=12/(a+a²)
8q²+8q+12q-12=0,q≠1 U q=0,q≠-1
8q²+20q-12=0
2q²-5q-3=0
D=25+24=49
q1=(5-7)/4=-0,5⇒a1=8/(1+0,5)=8:3/2=16/3
q2=(5+7)/4=3⇒a1=8/(1-3)=-4