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May 1, 2016
Posted by **Edward** on Friday, February 15, 2013 at 1:56am.

And please show working out to help me understand.

- MATHS GEOMETRY!!! URGENT PLEASE. -
**Steve**, Friday, February 15, 2013 at 5:09amif a,b,c = 10,17,21,

a^2 = b^2+c^2-2bc cos C, so

cosC = (17^2 + 21^2 - 10^2)/(2*17*21) = 15/17

so, sinC = 0.47

figure sinA and sinB the same way

If the altitudes from A,B,C are Ha,Hb,Hc, then

Hc = a*sinB = b*sinA

Figure the other altitudes in like wise.

OR--------

figure the area using Heron's formula.

Then since 1/2 c*Hc = area

Hc = 2*area/c

Since the area does not change, the shortest altitude is on the longest side.