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rearanging a maths equation, triangles and co-ordinates

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Reply 20
Avatar for Cypriots
Cypriots
12
CosA = b^2 + c^2 - a^2/ 2bc

so

CosA = 12^2 + 10^2 - 15^2/(2x10x12) = 0.079166666

cos-1 0.079166666

A = 85.5 1d.p

(basically you get the formula;

a^2 = b^2 + C^2 - 2bccosA

at the front of the booklet, so you rearrange this formula to get CosA at the front (or memorise this) to figure out angles.

the formula for angles; CosA = b^2 + c^2 - a^2/ 2bc
you then simply plug in all the values into your calc and get a number, then you cos -1 for the angle.
Reply 21
Avatar for Anon_123
Anon_123
OP
Cypriots
CosA = b^2 + c^2 - a^2/ 2bc

so

CosA = 12^2 + 10^2 - 15^2/(2x10x12) = 0.079166666

cos-1 0.079166666

A = 85.5 1d.p

(basically you get the formula;

a^2 = b^2 + C^2 - 2bccosA

at the front of the booklet, so you rearrange this formula to get CosA at the front (or memorise this) to figure out angles.

the formula for angles; CosA = b^2 + c^2 - a^2/ 2bc
you then simply plug in all the values into your calc and get a number, then you cos -1 for the angle.


Thank you! :woo:

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