Click and drag point A or point B to change the triangle. (Angle CAB is always a right 90° angle so C depends on A and B).
Find the value of cos(α) using your calculator. Use either

the cosine key and the size of the angle α or

just divide the sides to find the value of the fraction .

(Both ways of calculating should give you the same value.)

Can you make an isosceles triangle? What is the size of α? What is the value of cos(α)?

Can you make an equilateral triangle?

Can you make a 3, 4, 5 triangle with b=3, a=4 and c=5? What is the size of α? What is the value of cos(α)?

Can you make a 4, 3, 5 triangle with b=4, a=3 and c=5? What is the size of α? What is the value of cos(α)?

Can you make a triangle with α = 75°? What is the value of cos(75°). Write down the lengths of the sides a and c. Can you make a different triangle α=75°?