sec(780°) + cos(-540°) + sin(630°)
Any angle which is more than 360° can be reduced to a
smaller angle with the same trig functions by dividing
by 360° and taking the remainder, so
2 1 1
360)780 360)540 360)630
720 360 360
60 180 270
So the problem reduces to
sec(60°) + cos(-180°) + sin(270°)
Since cos(-q) = cos(q),
sec(60°) + cos(180°) + sin(270°)
The secant is the reciprocal of the cosine and cos(60°) = 1/2. So
sec(60°) = 2, cos(180°) = -1 and sin(270°) = -1, and the above is
2 + (-1) + (-1) = 0
Edwin
