I have recently read the problem named "Square of the distance function on a Riemannian manifold"([enter link description here][1]) and I am interested in the formula\ $ d^2(exp_{x_0}(tv),exp_{x_0}(tw))=|v-w|^2t^2-\frac{1}{3}R(v,w,w,v)t^4+O(t^5) $.\ However I can not solve it by myself. Can one give me a complete solution? [1]: https://mathoverflow.net/questions/215573/square-of-the-distance-function-on-a-riemannian-manifold