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[sharp sapphire]

i think it may be asking for double angle formulas? have you learned that yet?

[sharp sapphire]

20^2 + 21^2 = 29^2

so the hypotenuse is length 29

sin is opposite over hypotenuse

so sinA = 21/29

now do the square root of 841 :)

np

not sure, i think cos its a forum you dont have to