Question

How do you prove tan(180°-a) = -tan(a)?

Answer 1

We use the formula `: tan(A-B)=(tanA-tanB)/(1+tanATanB).`

`:. tan(180^o-a)=(tan180^o-tana)/(1+tan180^o*tana).`

But, `tan180^o=0.` Hence, we get `tan(180^o-a)=-tana.`