α = 0.5;β=0.4;
bo={0,0};
ba={Cos[α+β],0};
bb={Cos[α]*Cos[β],0};
bc={Cos[α+β],Sin[α]*Cos[β]};
bd={Cos[α]*Cos[β],Sin[α]*Cos[β]};
be={Cos[α+β],Sin[α+β]};
h=be-ba;
g=Graphics[{
{Black,Line[{bo,be}]},
{Black,Line[{bo,ba}]},
{Blue,Line[{ba,bb}]},
{Green,Line[{ba,bc}]},
{Red,Line[{bc,be}]},
{Brown,Line[{be,bd}]},
{Green,Line[{bb,bd}]},
{Blue,Line[{bc,bd}]},
{Black,Line[{bo,bd}]},
Text["1",0.5be+0.05h],
Text["α",0.2ba+0.04 h],
Text["β",0.15ba+0.1h],
Text["cos β",0.5bd+0.05(be-ba)],
{Brown,Text["sin β",0.93bd+0.3h]},
{Green,Text["cos β  sin α",1.12bb+0.2h]},
Text["α",0.795bd+0.45h],
{Red,Text["cos α  sin β",0.85ba+0.7h]},
Text["Proč je sin(α+β) = sin α cos β + cos α sin β",0.5bb+1.05h],
Text["Pavel.Pokorny@vscht.cz",0.55bb-0.1h]
}]