u/Sorry-Fruit1065

https://preview.redd.it/10jjttkrrb2h1.png?width=755&format=png&auto=webp&s=5176a6776efc89b32f9ba6eeb5120a4b9492892e

I understood the 2.14's first and third equations' derivations, but I still couldnt figure out second equation, cos h cos d one.

can someone please explain?

https://preview.redd.it/sygy1ksn992h1.png?width=907&format=png&auto=webp&s=ad7f2b6c6282c8d83afeeb83cac5c4bcf6b7de08

in my opinion, the angles are complied wrong(in my mind ofc), I thought plumb line should create an angle of q that q equals arctan(a^2*y/b^2*x), and angle j should be arctan(y/x) instead, but from what I see and understood from the book, the reverse of my statement is written, can you please help me to understand these?

q is the (fi)', j is the fi btw.

Hi fellas, I wanted to know how to prepare for IOAA properly, as I wanted to join this year.

I got silver medal at national level with some mediocre resources, but I definitely know it isnt enough for me, as I need to prepare better, to get even selected for IOAA.

I know only a few topics at astrophysics and I have experience at national olympiads for physics(couldnt manage to get medal yet, finalist)

What do you guys suggest me to prepare for IOAA and its tst?