Cracking the SAT Physics Subject Test

Sin 30° is 0.5, so because sinθ = a/5, we can figure out that

a = 5 sinθ = 5 sin30° = 5(0.5) = 2.5

We can use the Pythagorean theorem to figure out b, the length of the other side. Or,
if we are told that cos 30° is about 0.87, then since cosθ = b/5, we’d find that

b = 5 cosθ = 5 cos30° ≈ 5(0.87) = 4.4

This gives us

These values can be checked by the Pythagorean theorem, since

2.5^2 + 4.4^2 ≈ 5^2.