spherical triangle formula fail

[meems]

testing a spherical triangle formula with 2 sides equal length.

from https://en.wikipedia.org/wiki/Solution_of_triangles#Solving_spherical_triangles

where a and b and c are triangle sides, gamma is the adjacent angle between sides a b.

if a = b then

c = arccos(2cos a + 2sin a cos(gamma) )

let a = 1 radian
and gamma = Pi/3

then I get the parameter for the arccosine as 1.922, which is greater than 1 and therefore cannot be used. This breaks the formula. I'm doing something wrong. but i can't figure out what.

 

[Dr.Peterson]

testing a spherical triangle formula with 2 sides equal length.

from https://en.wikipedia.org/wiki/Solution_of_triangles#Solving_spherical_triangles

where a and b and c are triangle sides, gamma is the adjacent angle between sides a b.

if a = b then

c = arccos(2cos a + 2sin a cos(gamma) )

let a = 1 radian
and gamma = Pi/3

then I get the parameter for the arccosine as 1.922, which is greater than 1 and therefore cannot be used. This breaks the formula. I'm doing something wrong. but i can't figure out what.

To start, cos(a) cos(a) is not equal to 2 cos(a)! Try fixing that and the sine, and see if things work better.