sin²α + cos²α = 1
sinα = y
cosα = x
tgα = sinα/cosα
ctgα = cosα/sinα

ա) cosα = 1/2
sin²α + 1/2 = 1
sin²α = 1 — 1/4 = 3/4
sinα = √3/2

բ) cosα = -3/5
sin²α + 9/25 = 1
sin²α = 1 — 9/25 = 16/25
sinα = 4/5

գ) cosα = -1
sin²α + 1 = 1
sin²α = 0
sinα = 0

ա) sinα = √3/2
3/4 + cos²α = 1
cos²α = 1/4
cosα = 1/2

բ) sinα = 1/4
1/16 + cos²α = 1
cos²α = 1 — 1/16 = 15/16
cosα = √15/4

գ) sinα = 0
0 + cos²α = 1
cos²α = 1
cosα = 1