# Geometry Problem 1287

### Elements: Isosceles Triangle, 40-100-40 Degrees, Congruence,
Area, Metric Relations, Measurement.

In an isosceles triangle ABC, the measure of angle B is 100 degrees, AB =
BC = a, and AC = b. Prove that: (1) a^{3} + b^{3} = 3a^{2}b; (2)
.

*This entry contributed by Sumith Peiris, Moratuwa, Sri Lanka.*

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