Ma'am I'm sorry i couldn't attend this class (april 21st trigonometric functions) as i was out of station.So i watched the recorded video of the class and i did no understand the eg of sec(570) which you did freehand.I haven't understood how it can be written as (5*90+30) .Also since it falls in the 2nd quadrant and since sec is changed to cosec, shouldn't the answer be cosec(30) instead of being -cosec(30)?

P.S the class is very interesting.Thank you.:)

    sec 570°=sec 540°+30°=sec6×90°+30°=sec6×π2 + π6=sec3π+π6=- sec π6         as, sec 3π+θ = - sec θ=-1cosπ/6=-13/2=-23

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