Law of Tangent

Why is the Law of Tangent not taught in any trig course?

 

The laws of tangent (Law of Tan) describes the relation between difference and sum of sides of a right triangle and tangents of half of the difference and sum of corresponding angles. It represents the relationship between the tangent of two angles of a triangle and the length of the opposite sides.
see the formulas:
https://byjus.com/maths/law-of-tangents/

note, in proof it all comes to sin and cos
since tan(x)=sin(x)/cos(x), it's much easier to use law of sin and cos

 

Interesting. It is easier to avoid the Law of Tangent. Can you work out one example using this law in trigonometry?

 

on that link above is one example

for a triangle ABC with sides a, b and c respective to the angles A , B and C is given by,

(a−b)/(a+b)=tan((A−B)/2)/tan((A+B)/2)
Therefore,

(5−3)/(5+3)=tan((A−B)/2)/tan(180°-96°)
2/8=tan((A−B)/2)/tan(84°) ............cross multiply
2*tan(84°)=8tan((A−B)/2)
=>tan(1/2(A−B))=(2/8)tan(42°)=0.2251
=>(1/2)(A−B)=12.7
=>A -B = 25.4°

 

Very good. Thanks.