Answer:
8 × sin(35)
Explanation:
remember the trigonometric norm circle and the triangle inside describing with its sides the trigonometric function values of the angle at the center of the circle.
sine is the vertical side, cosine is the horizontal side.
and the longest side really creating that angle at the center is the radius (going all the way from the center to the circle arc).
do not forget, the trigonometric functions sine, cosine, ... deliver values for the norm circle only (radius = 1).
for any circle larger or smaller these function values need to be multiplied by the actual radius to get the actual side lengths of the triangle.
now, we are allowed to rotate or twist/turn a given right-angled triangle to be oriented like the basic trigonometric triangle.
in our case we can simply flip things upside-down.
and we see, BC is simply sine of 35° (multiplied by the radius 8).
it does not matter that it is originally pointing down. it is for the angle 35°, and sine of angles 0° <= angle <= 180° must be positive.