find the acute angle between the lines:
x - 2y + 1 = 0
and
y = 5x - 4
1.
2. The angle between the first line and the horizontal is . Then you know that .
The angle between the second line and the horizontal is . Then you know that .
3. The angle which is included by the 2 lines is
4. Use the property:
5. Plug in the values you know. You should come out with:
This formula belongs to a set of equations concerning the trigonometric functions of sums (or differences) of angles.
I learned it nearly 50 years ago - so I don't get it but I have ithow do you get it?
Fine!how does it work?
As I've mentioned you only have to plug in the known values:
Now you can calculate the angle using the or function.