Explanation:
just think back to the standard circle of radius = 1.
there the trigonometric functions are all represented as sides of right-angled triangles, where the radius is the baseline.
just like the triangle we are seeing here.
the only difference : the baseline (radius) is 17 and not 1.
and that is fine. everything is as in the standard circle, but multiplied by the radius (which is also true for the standard circle, but multiplying by 1 does not change anything, right ?).
a)
angle A is or focus. so, just imagine the triangle turned counterclockwise by 90° (so that AC is horizontal and CB is vertical).
do you see it now ?
sin is the vertical leg, cos the horizontal leg. and the leg lengths here are the standard functions multiplied by the radius.
so,
17 × sin A = 8
sin A = 8/17 = 0.470588235... ≈ 0.47
b)
17 × cos A = 15
cos A = 15/17 = 0.882352941... ≈ 0.88
c)
now B is our focus. imagine the triangle being mirrored at point B, so that B is left, and AC is right. your see it now ?
tan B = sin B / cos B
sin B = 15/17 = 0.882352941... ≈ 0.88
cos B = 8/17 = 0.470588235... ≈ 0.47
tan B = 15/17 / 8/17 = 15/8 = 1.875 ≈ 1.88
d)
cos B = 8/17 = 0.470588235... ≈ 0.47