Use the cosine law to find angle Q, the smallest angle
10^2 = 17^2 + 21^2 - 2(17)(21)cosQ
cosQ = 630/714 = ....
Q = .....
sinQ = h/17
h = 17(sinQ)
In △PQR, PQ = 17 in, PR = 10 in, QR = 21 in. Find the altitude from P to the side QR.
2 answers
use the law of cosines to get, say angle R.
17^2 = 10^2 + 21^2 - 2*10*21 cosR
cosR = 3/5
Now find the altitude h from P using
h/10 = sinR = 4/5
h = 8
17^2 = 10^2 + 21^2 - 2*10*21 cosR
cosR = 3/5
Now find the altitude h from P using
h/10 = sinR = 4/5
h = 8
1 answer