When is spherical trigonometry introduced and how does it apply to physics?

[parshyaa]

• When do we learn about spherical trigonometry and what are its application(mostly in physics)
• I have read a formula named versed sine = 1- cos(θ) in the trigonometry book by S.L loney, I tried it on google to know more about it and the research made me shocked, haversine(half of versed sine) formula is used for navigation, and it comes under spherical trigonometry, therefore I want to know more about it , I am in 11th grade, is there any friendly book on this topic which can be friendly for me. Thanks.

 

[phinds]

• When do we learn about spherical trigonometry and what are its application(mostly in physics)
• I have read a formula named versed sine = 1- cos(θ) in the trigonometry book by S.L loney, I tried it on google to know more about it and the research made me shocked, haversine(half of versed sine) formula is used for navigation, and it comes under spherical trigonometry, therefore I want to know more about it , I am in 11th grade, is there any friendly book on this topic which can be friendly for me. Thanks.

I'm sure it very likely has practical applications but I swear, when I took it many years ago, I was CONVINCED that its primary application was to give me a headache.

 

[micromass]

what are its application(mostly in physics)

We live on a sphere.