A question on the proof of induced metric from Riemannian metric

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The following Picture is the proof of "distance function on Riemannian manifold is a metric".

Page-4

How the author deduced that length of any curve from $p$ to the boundary of given ball is at least $r/\lambda_0$?

Thanks.

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Write down the integral for the length of any path from $p$ to the boundary of the ball (presumably they're choosing $r$ so that the point $q$ lies outside the ball). If you have a symmetric matrix $A(x)$ whose smallest positive eigenvalue is at least $\lambda_0$, what can you say about $\sqrt{u^\top A(x) u}$ for any vector $u$? Now integrate the appropriate expression to get the length of the path, and what's the lower bound you have?