A symmetrical roof truss has a span of 8m and a rise of 3.4m. calculate the angle at which the roof is pitched

Question

Can you help me work this out please

Answer 1

Look at the truss as a triangle measuring 4m to the centre of the span from which point you can raise a perpendicular of 3.4m.  You now have two sides of a right-angled triangle; the Opposite and the Adjacent to the angle you wish to find.  Thus:

Tan X = 3.4/4 = 40.36 degrees

So much for an Oxford First!

Answer 2

Whoa I got totally lost looking for the Inverse Tan function in OOCalc!

Anyway, Tan(x) = O/A

x = angle = unknown

O = Opposite side = 3.4 (the height)

A = Adjacent side = 4 (half the total width of the span)

Why half? because it then forms a right angled triangle so we can use the simple Trig formula above.

3.4/4 = 0.85

InverseTan 0.85 gives 40.36453657...... in degrees.

So just put that to however many Significant figures you want.

eg: for 3 s.f,

ANSWER = 40.365 degrees to horizontal.

By the way, my old maths teacher always used to say it's worth drawing a sketch if you're not sure about a question. It'll help you visualise the problem.

Answer 3

the angle of the roof is 75.95 degrese