Solve 5 cos^2 A + sin2A=0

Question

For 0 《 A 《 360○

Answer 1

The trigonometric equation is .

Divide each side by  .

The function tan A  has period of 2π , first find all solutions in the interval [ 0 , 2 π ] .

The function tan A is positive in first and third quadrants.

In first quadrant :

.

In third quadrant :

.

The function tan A is negative in second and fourth quadrants

In second quadrant :

In fourth quadrant :

The solutions are in the interval [ 0 , 2 π ].