Hello, UltraGirl!

Those two arctan expressions look similar . . . that's a clue.Prove: .

. .

Look at the right triangles . . .

Code:* * * | * | * | * β | * | 4 * | 4 * | * | * α | * | * - - - - - * * - - - - - * 3 3

See it?

The two angles are in the same right triangle.

. . They are complementary: .

That is: .

Substitute into the left side:

. .

. . . . .

. . . . .

. . . . .