# How do you find the solution for #tan^2 A - 3tanA - 4 = 0# for [-90,0]?

##### 1 Answer

Oct 23, 2015

Solve tan^2 A - 3tan A - 4 = 0 for (-90, 0)

Ans:

#### Explanation:

Call tan A = t, we get a quadratic equation:

t^2 - 3t - 4 = 0.

Since (a - b + c = 0), use Shortcut. The 2 real roots are t = -1 and

t = -c/a = 4.

The trig unit circle and Trig Table of Special Arcs give:

a. t = tan A = -1 -->

b. t = tan A = 4 --> A = 75.96 and A = 75.96 + 180 =

Inside the interval (-90, 0) there is only one answer:

or