the festival is almost ready
nd a venue
t out secur
3) Sound system!!
Are you sure it’s OK to be
estimating angles like this? Don’t we
always need to work out exactly what
the angle is?
A:If the problem or question requires
a precise answer along the lines of “what
is angle x,” then you’ll need to find the
angle exactly, but sometimes it’s possible
to solve a problem just by knowing roughly
what an angle is. For example, is it a right
angle? Or maybe just is it acute or obtuse?
And this is isosceles only, yeah?
A:Yes, this technique only works
reliably for an isoceles triangle—where
two angles and two sides are the same. An
equilateral triangle is an isoceles triangle
with an extra matching side, so it works
for those, too, but then they’re pretty easy
What if I only know the base and
the side, or the base and the height?
A:Sometimes that’s all you need. Any
time the base is greater than twice the
height you know you’ve got an angle more
than 90º.You really only need both for that
tricky zone between 60º and 90º.
But don’t worry—if you’ve got two out of
three for the base, side, and height lengths,
you can use the good old Pythagorean
Theorem to find the other. (This only works
for right and isoceles triangles—don’t
try it on a scalene triangle or you’ll come
OK—but how do I remember this?
I’m bound to get mixed up about the
base and sides and and which is greater
and less than which! I’m not a computer
A:It’s almost certainly easier to
remember the zones on the graph than it is
to remember the inequalities.
So, sketch that graph, mark what you know
about the 60º and 90º triangles on it, and
label the zones.
Really? You think I could draw it
just like that?
A:Go on…give it a shot on a scrap of
paper now. It’s a really time efficient way to
check your answers in an exam by the way.
180 Chapter 4