Question

Помогите плиз!!!!!!!!!!

Answer 1

Ответ:

Объяснение:

1.

sin (a)= $\sqrt{1-\frac{1}{49} } =-\frac{4\sqrt{3} }{7}$  (знак "-" т.к. $\alpha$∈$\frac{3\pi }{2} ;2\pi$)

tg (a)=$-4\sqrt{3}$

ctg (a)= -$\frac{1}{4\sqrt{3} }$

2.cos(a)=$\sqrt{1-\frac{4}{25} }$=$\frac{\sqrt{21} }{5}$

tg (a)=$\frac{2}{\sqrt{21} }$    ctg (a)=$\frac{\sqrt{21} }{2}$

($\frac{2}{\sqrt{21} }$+$\frac{\sqrt{21} }{2}$)*$\frac{\sqrt{21} }{5}$=$\frac{5}{2}$=2.5

3.

ctg^2(a)=$\frac{cos^2(a)}{sin^2(a)}$

cos^2(a)-sin^2(a)+1=cos^2(a)-sin^2(a)+sin^2(a)+cos^2(a)

cos^2(a)+cos^2(a)=2cos^2(a)

4.

$\frac{1}{sin^{2}(a) } =ctg(a)+1$

cos^2(a)-ctg^2(a)-1+ctg^2(a)=cos^2(a)-sin^2(a)-cos^2(a)=-sin^2(a)