# Simple Cosine

- Author:
- Linda Fahlberg-Stojanovska

- Topic:
- Cosine

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
.

- 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°?