Question

Please help me trigonometry

Answer 1

Hello,

28:

$\left \{\begin{array}{ll} x&=-1+3cos(\theta)\\ y&=2+3sin(\theta)\\ \end{array} \right .\\\\ \left \{\begin{array}{ll} x+1&=3cos(\theta)\\ y-2&=3sin(\theta)\\ \end{array} \right .\\\\ \left \{\begin{array}{ll} (x+1)^2&=9cos^2(\theta)\\ (y-2)^2&=9sin^2(\theta)\\ \end{array} \right .\\\\ \Rightarrow\ (x+1)^2+(y-2)^2=9cos^2(\theta)+9sin^2(\theta)\\ \Rightarrow\ (x+1)^2+(y-2)^2=9(cos^2(\theta)+sin^2(\theta))\\ \Rightarrow\ (x+1)^2+(y-2)^2=9$

Circle of center (-1,-2) and radius 3.