Homework about plane engineering drawing

[A dummy progression]

Homework Statement

We give :

Frame: 150 × 180 (units in mm)

The line a and the point O.

Vertical projection of line a is (0 , 60) ; (150 , 170)
Horizontal projection of line a is (0 ,140) ; (150 , 40)
Vertical projection of point O (50 , 140)
Horizontal projection of point O (- ; 50)

We ask:

To build in the plan (O , a) the isocele triangle OAB ; the main vertex of this triangle is O and the base AB = 40 mm knowing that the AB side is carried by a and that A is the lowest vertex on the line a.

Note : Do all this using changes of projection plane

Relevant Equations

Real measure of a plabe figure using changes of projection plane

Hello, i wasn't in enginnering drawing class since 2 weeks because i was sick and my high school teacher told me to do this homework.
This is what I've done so far

I did not build the triangle 'cause i am not sure.
Please, i just want that someone accompanies me with steps by steps explanation because its the only one work that will decide if i fail class this period and we'll have semester exam next week.

But I've an idea about this homework :
1) drawing a frontal line of plan (O,a) crossing O and using it as a generatrice of the plan
2) find point B

And then i am puzzled about using changes of projection planes to build the isocele triangle.

Your help is welcome.

 

[Lnewqban]

Where is line a named?
Are the 150 mm vertical or horizontal?
What is the first value for the horizontal projection of point O?

 

[A dummy progression]

Where is line a named?
Are the 150 mm vertical or horizontal?
What is the first value for the horizontal projection of point O?

O(-,50)
Frame : 150 mm horizontal , 210 mm vertical
The two longest lines are the projections of line a and their names are close the frame

 

[Lnewqban]

Regarding this problem, what have you learned so far in that enginnering drawing class?

Sorry, what is the first value for the horizontal projection of point O?
The minus sign in (-,50) seems to be a typo.
According to your drawing, it should be (50,50); could you confirm?

 

[A dummy progression]

Regarding this problem, what have you learned so far in that enginnering drawing class?

Sorry, what is the first value for the horizontal projection of point O?
The minus sign in (-,50) seems to be a typo.
According to your drawing, it should be (50,50); could you confirm?

Yes it's (50,50)

 

[Lnewqban]

Yes it's (50,50)

Thank you.
Do you understand the meaning of these two orthographic projections?

 

[A dummy progression]

Thank you.
Do you understand the meaning of these two orthographic projections?

View attachment 296652

View attachment 296654

These lines represent planes?

 

[Lnewqban]

The top yellow rectangle represents the vertical plane on which the horizontal projection is drawn.
The bottom yellow rectangle represents the horizontal plane on which the vertical projection is drawn.

As you can see in the isometric drawing, the line joining both, vertical and horizontal planes, is the x-y line about which they are pivoted or opened from the normal 90-degree angle to each other.

That is the most universal way of representation, but perhaps your course teaches a different way; therefore, my previous question about what you have learned so far.