Explanation:
Now we know that
sec?# -tan? e=1
So tanZ0 =sec20 - 1
So the left of the given equation will be
sec220 + sec240 +sec280-3
SO
1/cos220+1/cos249+1/cos280-3
Remember sec 0= 1/cosf
SO
= since sec0 = 1/cos©
we have
= 1.1324 + 1.7040 + 33.1634 - 3
= 35.9998 - 3
= 33