Boris Hasselblatt, Professor—on leave from the Department of Mathematics

Tufts University
Medford, MA 02155-5597
Email:

#### Research:

Books I have written or edited:

Journals and book series on whose boards I serve:

Some articles:

• Contact Anosov flows on hyperbolic 3-manifolds
• Longitudinal foliation rigidity and Lipschitz-continuous invariant forms for hyperbolic flows
• Zygmund strong foliations in higher dimension
• Lipschitz-continuous invariant forms for algebraic Anosov systems
• Pointwise hyperbolicity implies uniform hyperbolicity
• The Sharkovsky Theorem: A natural direct proof
• Entropy
• Degree
• Zygmund rigidity
• Hyperbolic dynamics
• Nonuniform hyperbolicity
• Pesin entropy formula
• Select publication information is available if you or your institution have a MathSciNet subscription:
• My publications, reviews, select citations
• A select citation count
• Reviews of some of my publications; a stale version of this is here for those without an MR subscription.
• A small sample of the reviews I have written
• Find my current Erdös number

Tufts Now

#### Quoted

Science Magazine on draft NSF guidance on broader impacts

#### Videos

The Big Picture
Why I am away in the summer
Viewing your future as a PhD student
The Poincaré Institute for Mathematics Education at Tufts University
Tufts University Baccalaureate Service 2012
Tufts University Baccalaureate Service 2011
Tufts University Commencement 2012
Tufts University Commencement 2011
Tufts Presidential Inauguration 2011
Trinity Church in Boston reopens after blasts

#### Miscellaneous

AMS Math MomentsScience News

#### Salient values of trigonometric functions

I noticed this pattern in the early 1990s but learned that I am far from being the first to have done so (Jean-Luc Eveno heard this some 20 years earlier from a teacher and surmises that it has been teachers' lore for generations before):
 $$x$$ in degrees: $$0^\circ$$ $$30^\circ$$ $$45^\circ$$ $$60^\circ$$ $$90^\circ$$ $$x$$ in radians: $$0$$ $$\displaystyle\frac\pi6$$ $$\displaystyle\frac\pi4$$ $$\displaystyle\frac\pi3$$ $$\displaystyle\frac\pi2$$ "Label": $$0$$ $$1$$ $$2$$ $$3$$ $$4$$ $$\sin(x)$$: $$\displaystyle\frac{\sqrt0}2$$ $$\displaystyle\frac{\sqrt1}2$$ $$\displaystyle\frac{\sqrt2}2$$ $$\displaystyle\frac{\sqrt3}2$$ $$\displaystyle\frac{\sqrt4}2$$
If you have seen this published anywhere I'd be interested in knowing.