How long is the base of an isosceles triangle if the equal sides are 20 cm long and the base angles measure 52 degrees

40cos(52) or 40sin(38)

Do you see why?

If the base equals "b" and the two congruent sides equal "s":

A perpendicular bisector of the base equals "b/2" and creates two congruent right triangles.

The third angle equals 76, and with a perpendicular bisector equals 38 in one of the congruent right triangles.

-So- sin38= (b/2)/20

Solve for "b" to find length of the base.