documentclass[border=5mm]{standalone}
usepackage[dvipsnames]{xcolor}
usepackage{tkz-euclide}
usetkzobj{all}

begin{document}

begin{tikzpicture}
% Set up the canvas
tkzInit[xmin=0, xmax=7, ymin=0, ymax=4.5]

% Clip things outside the canvas
tkzClip[space=0.5]

% Define two starting points on a horizontal
tkzDefPoint(0,0){A}
tkzDefPoint(5,0){C}

% Find a point perpendicular to A,C
tkzDefPointWith[orthogonal,K=-0.9](C,A)
% Give that new point a name
tkzGetPoint{B}

% Find the point on the intersection between AC and a circle centered on A passing through B
tkzInterLC(A,C)(A,B)
tkzGetSecondPoint{B'}

% It doesn't really make sense to fill the sectors, since we're concerned with angles, not areas
%tkzDrawSector[fill=BrickRed!40, draw=none](A,B')(B)
%tkzDrawPolygon[fill=gray!20, draw=none](A,C,B)
%tkzDrawSector[fill=Dandelion!60, draw=none](A,C)(B)

% Draw the segments
tkzDrawSegments[gray](A,B A,B')
tkzDrawSegment[black, very thick](C,B)

% Draw the arcs
tkzDrawArc[draw=BrickRed, very thick](A,C)(B)
tkzDrawArc[draw=MidnightBlue, very thick](A,B')(B)

% Label the points
tkzLabelPoints[below left](A)
tkzLabelPoints[above](B)
tkzLabelPoints[below](C)

% Get the radii of the sectors so we can place the sector labels nicely
tkzCalcLength[cm](A,B)tkzGetLength{rAB}
tkzLabelAngle[pos=(rAB), anchor=south west, text=MidnightBlue](B,A,C){$theta$}

tkzCalcLength[cm](A,C)tkzGetLength{rAC}
tkzLabelAngle[pos=(rAC), anchor=north east, text=BrickRed!70!black](B,A,C){$thetacostheta$}

tkzLabelSegment[anchor=west](C,B){$sintheta$}
end{tikzpicture}


end{document}