Draw the base line AB of the length 6 cm.
Use your compass to make a circle with centre at point A and the radius 4 cm.
Use your compass to make a circle with centre at point B and the radius 3 cm.
In the point of intersection between the two circles, you'll find the point C.
Complete the triangle by drawing the lines between all three points, as shown below.
Now, from the above construction we see that the measure of angle A is 36∘.