Solution: Given that cos(x) = -(135) = 13−5 and π/2≤x≤π
∴ x is in second quadrant.
{ we know that if cos(x) = hb then sin(x) = ha , where a = h2−b2 & tan(x) = cos(x)sin(x) }
therefore if we compare with the given cos(x) value we get:
b = -5 & h = 13
⟹ a = 132−(−5)2
⟹ a = 169−25
⟹ a = 144
⟹ a = ± 12
in the second quadrant value of sin(x) is always positive.
therefore, we take a = 12
sin(x) = ha = 1312
tan(x) = cos(x)sin(x) = −5/1312/13 = -512
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