Question

10.(a) Copy and complete the table of values for y = 2cos x − sin x, 0° ≤ x ≤ 300°.
10.(b) Using scales of 2cm to 30° on the x-axis and 2cm to 1 unit on the y-axis, draw the graph of y = 2cos x − sin x for 0° ≤ x ≤ 300°.
10.(c) Use the graph to find the value(s) of x for which: (i) 2cos x − sin x = 1; (ii) tan x = 2.

Accepted Answer

(a) Computed values: x=0°:2.00, 30°:1.23, 60°:0.13, 90°:−1.00, 120°:−1.87, 150°:−2.23, 180°:−2.00, 210°:−1.23, 240°:−0.13, 270°:1.00, 300°:1.87.
(b) Plot these points and draw a smooth curve.
(c)(i) Reading where y=1 on the graph gives x≈37° and x=270°.
(ii) tan x = 2 corresponds to x≈63° and x≈243° (where the curve crosses the tan x=2 line).

WAEC Mathematics 2018 Theory — Question 16

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