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If cosθ + secθ = $$\sqrt 3 ,$$ then the value of (cos3θ + sec3θ) is?
Answer & Solution
Correct Answer:
Option
C
$$\eqalign{
& {\text{cos}}\theta + \sec \theta = \sqrt 3 \cr
& {\text{Cubing both sides}} \cr
& {\text{co}}{{\text{s}}^3}\theta + {\sec ^3}\theta + 3{\text{cos}}\theta \sec \theta \left( {{\text{cos}}\theta + \sec \theta } \right) = 3\sqrt 3 \cr
& {\text{co}}{{\text{s}}^3}\theta + {\sec ^3}\theta + 3\sqrt 3 = 3\sqrt 3 \cr
& {\text{co}}{{\text{s}}^3}\theta + {\sec ^3}\theta = 0 \cr} $$
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