# Inserting label to a Plot

I have the following figure

Given by the Following code

pic3 := Plot[0.7 + 0*x, {x, -0.5, 1}]
pic4 := ListLinePlot[
Thread[List[0.8 & /@ Range[0, 1], Range[-0.2, 1]]]]

pic5 := Graphics[Line[{{0, 0}, {0, 1}, {1, 0}, {0, 0}}]]
Show[pic5, pic4, pic3, PlotRange -> {{-1, 1}, {-1, 1}}]


I would like to add 2 brackets one that said $$\alpha$$ between $$(0,0)$$ and the cut in $$y$$-axis and another that said $$\beta$$ between $$(0,0)$$ and the cut at the $$x-$$Axis. Is this possible ? Thanks in advance .

{a, b} = MapThread[Graphics[{#, Disk[], White,
Inset[Style[#2, FontSize -> Scaled[.5]]]}, ImageSize -> 40] &,
{{Blue, Red}, {"α", "β"}}];

Deploy @ DynamicModule[{pt1 = {0., .8}, pt2 = {.8, 0}},
Graphics[{EdgeForm[Black], FaceForm[], Triangle[],
FaceForm[Opacity[1]],
Locator[Dynamic[pt1, (pt1 = {#[[1]], .8}) &], a],
Locator[Dynamic[pt2, (pt2 = {.8, #[[2]]}) &], b]},
GridLines -> {{.8}, {.8}},
GridLinesStyle -> Directive[Thick, ColorData[97]@1]]]


For a different approach, beginning with version 12 you can use the EXPERIMENTAL function GeometricScene

Clear["Global*"]

Show[
GeometricScene[
{"O" -> {0, 0},
a -> {0, 1}, b -> {1, 0},
α -> {0, 0.7}, β -> {0.8, 0},
α2 -> {1.5, 0.7}, (*
chosen outside the plot range *)
β2 -> {0.8, 1.5}},(*
chosen outside the plot range *)
{Triangle[{a, b, "O"}],
InfiniteLine[{α, α2}],
InfiniteLine[{β, β2}]}]
["Graphics"],
PlotRange -> {{-0.5, 1.1}, {-0.2, 1.1}}]


Or for a dynamic scene

Manipulate[
Show[
GeometricScene[
{"O" -> {0, 0},
a -> {0, 1}, b -> {1, 0},
"α" -> {0, α}, "β" -> {β, 0},
α2 -> {1.5, α}, (*
chosen outside the plot range *)
β2 -> {β, 1.5}},(*
chosen outside the plot range *)
{Triangle[{a, b, "O"}],
InfiniteLine[{"α", α2}],
InfiniteLine[{"β", β2}]}]
["Graphics"],
PlotRange -> {{-0.5, 1.1}, {-0.2, 1.1}}],
{{α, 0.7}, 0, 1, 0.025, Appearance -> "Labeled"},
{{β, 0.8}, 0, 1, 0.025, Appearance -> "Labeled"}]
`