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Q6. A vertical aerial, AB, is 18m high, standing on ground which is inclined 10° to the horizontal.

A stay connects the top of aerial A to a point C on the ground 12 m downhill from B, the foot of the aerial.

Calculate EACH of the following:

(i) the length of stay AC;     (5)

(ii) the angle the stay AC makes with the ground;          (3)

(iii) the length of a second stay which connects to a point D, 6m from the top of the aerial to point C.          (2)

(b) A current, i amps, is given by I = 5cos(100pt + 25), where t is the time in seconds.

Calculate the earliest time, t > 0, for which the current I = 2amps.       (6)