Question

How can we find (theta) cos (theta+20) =cos (theta)?​

Answer 1

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the cosine of an angle is the side adjacent to the angle divided by the hypotenuse of the triangle. In the diagram, the adjacent side is a and the hypotenuse is c , so cosθ=ac . To find θ , you use the arccos function, which has the same relationship to cosine as arcsin has to sine

Answer 2

Step-by-step explanation:

Given that sinθ+cosθ=1

now squaring both side we have

(sinθ+cosθ)

2

=1

2

sin

2

θ+cos

2

θ+2sinθcosθ=1

1+2sinθcosθ=1 (sin

2

θ+cos

2

θ=1)

2sinθcosθ=0

sin2θ=0 (sin2θ=2sinθcosθ)