sin^2a*sinb/cosb=sin^2b*sina/cosa.

∵ SINA ≠ 0, COSB ≠ 0, both sides of the ∴ equation are the same as the common divisor of sinA*sinB.

∴sinA/cosB=sinB/cosA.

sinAcosA=sinBcosB。

Use about *2 to get

∴sin2A=sin2B.

2A=2B。 ( 1);

D: a = B。

∴△ABC is an isosceles triangle;

Or: sin2a = sin (180-2b) (2) Trigonometric functions with the same name have the same value, and their angles are equal or complementary.

It is obtained that 2a = 180-2b, 2a+2b = 180, and a+b = 90.

△ ABC is a right triangle.

Think slowly, find out the relationship between the sides of the triangle, and carefully calculate O(∩_∩)O~