Drawing a triangle, with angles inside, inside a circle and other details

Question

I am trying to draw a figure similar to this one 
This is the code for that figure that I've done so far
documentclass{article}
usepackage[utf8]{inputenc}

usepackage{tikz}
usepackage{graphicx}
usepackage{amsmath}
usepackage{amssymb}
usepackage{xcolor}

begin{document}

begin{tikzpicture}
    %coordinate system
    draw[thick,->] (0,-5) -- (0,5)node[above left]{$y$};
    draw[thick,->] (-5,0) -- (5,0)node[below right]{$x$};
    
%circle
draw (4,0) arc (0:360:4)node[ below]{$ $};

%dots % their lines
draw[red] (0,0) -- (2.8,2.9)  node[circle,red,fill,inner sep=3pt]{} node[above right]{$Q=(cos v,sin v)$};

draw[blue] (0,0) -- (-2.8,2.9)  node[circle,blue,fill,inner sep=3pt]{} node[above left]{$P=(cos u,sin u)$};

%line joining both dots
draw[magenta] (-2.8,2.9) -- (2.8,2.9) node[midway, above left ]{$d$};

%angles
draw (2,0) arc (0:134:2)node[midway,above right]{$u $};

draw (1,0) arc (0:45:1)node[midway,above right]{$v $};

end{tikzpicture}

end{document}

How can I draw the arrows for the direction of the angles?
And also how can I add the label for the circle, it's supposed to be a unit circle, I wanted to draw an arrow indicating that  the equation $x^2+y^2=1$ is that circle.
Could someone please help?
Thank you in advance.
Edit.
The label for the circle without arrow:
%circle
draw (4,0) arc (0:360:4)node[very near end, below right]{$x^2+y^2=1$};
Edit2.
So far, the image is this, which looks decent :) I think.

Torbjørn T. · Accepted Answer

Arrow tips for arcs are added the same way as arrow tips to other paths, so do exactly the same as you did for the axes: [->]
For the equation: add the node with e.g. node (eq) at (x,y) {...}; with suitable values for x and y, or node (eq) at (angle:radius) {...}; to use polar coordinates instead of Cartesian coordinates. Having named the node eq, you can draw an arrow from it to the circle with e.g. draw [->] (eq) -- (-20:4);, again using polar coordinates.
In the code below I used polar coordinates to place the P and Q nodes as well, and included a style for the dots, and used labels for the P/Q labels. Obviously your method with a second node works fine as well, so this is mostly a matter of personal preference I guess. Polar coordinates are quite convenient in this case though. Oh, and I used the circle construct to make the circle instead of an arc.

documentclass{article}%
usepackage[utf8]{inputenc}

usepackage{tikz}

begin{document}

begin{tikzpicture}[dot/.style={circle,fill,inner sep=3pt, outer sep=0}]

%coordinate system
draw[thick,->] (0,-5) -- (0,5) node[above left]{$y$};
draw[thick,->] (-5,0) -- (5,0) node[below right]{$x$};
    
%circle
draw (0,0) circle[radius=4cm];

%dots 
path [red]  (45:4)  node[dot, label={above right:{$Q=(cos v,sin v)$}}] (p) {};
path [blue] (135:4) node[dot, label={above left:{$P=(cos u,sin u)$}}] (q) {};

%line joining dots
draw[magenta] (p) -- (q) node[midway, above left ]{$d$};
draw [red]    (0,0) -- (p);
draw [blue]   (0,0) -- (q);

%angles
draw [->] (2,0) arc (0:135:2) node[midway,above right] {$u$};
draw [->] (1,0) arc (0:45:1)  node[midway,above right] {$v$};

node (eq) at (-10:6cm) {$x^2 + y^2 = 1$};    
draw [->] (eq) to[bend left] (-30:4);

end{tikzpicture}

end{document}

Drawing a triangle, with angles inside, inside a circle and other details

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