- #1

- 409

- 0

When I'm working out a maths or physics problem I always find myself questioning whether I should work out the equation as I go along or should I re arrange it and do it in one step with my calculator?

For example if I was to use the cosine rule for triangles,

a

to solve a triangle for angle A with sides a, b and c as 20, 30 and 40 respectively.

Is this better written out as,

a

20

400=900+1600-2400cosA

-2100=-2400cosA

7/8=cosA

A=cos

A=29.0°(1D.P.)

or

a

A=cos

A=cos

A=cos

A=29.0(1D.P.)

Thanks

AL

For example if I was to use the cosine rule for triangles,

a

^{2}=b^{2}+c^{2}-2bccosAto solve a triangle for angle A with sides a, b and c as 20, 30 and 40 respectively.

Is this better written out as,

a

^{2}=b^{2}+c^{2}-2bccosA20

^{2}=30^{2}+40^{2}-2*30*40*cosA400=900+1600-2400cosA

-2100=-2400cosA

7/8=cosA

A=cos

^{-1}(7/8)A=29.0°(1D.P.)

or

a

^{2}=b^{2}+c^{2}-2bccosAA=cos

^{-1}[itex]\left(\frac{b^{2}+c^{2}-a^{2}}{2bc}\right)[/itex]A=cos

^{-1}[itex]\left(\frac{30^{2}+40^{2}-20^{2}}{2*30*40}\right)[/itex]A=cos

^{-1}(7/8)A=29.0(1D.P.)

Thanks

AL

Last edited: