69.
In the diagram, MNR is a tangent to the circle centre O at N and ∠NOS = 108°. Find ∠OSN
A.
72°
B.
32°
C.
36°
D.
18°
Correct answer is C
The sum of angles in a triangle = 180º
(180 - 108)º = 72º
Isosceles triangle has both two equal sides and two equal angles.
∠OSN = ∠SON = 722
= 36º
70.
Given that sin (5x-28)° = cos (3x-50)", 0°≤ x ≤ 90°, find the value of x.
A.
39
B.
32
C.
21
D.
14
Correct answer is B
using the trial method by inserting each option in the equation.
Inserting 21º: sin([5 x 21] - 28) = cos([3 x 21] - 50)
sin(105 - 28) = cos (63 - 50)
sin 77º = cos 13º
where:
sin 77º = 0.9744
cos 13º = 0.9744
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