what is the formula for these triangles ?

Answer 1

sin 15 = sin 30/2 = sqrt ([1 -cos 30]/2)

cos 15 = cos 30/2 = sqrt( [1 + cos 30]/2)
but
we know cos 30 = (sqrt 3)/2
plug in
then
sin (90-t) = cos t
and cos (90-t) =sin t
to get sin and cos of 75
if you need tangents use tan = sin/cos

Answer 2

ok ty alot