Q5 of 21 Page 113

Fill in the blanks.

i.


ii.


iii.

i. We know the following identity,

sinθ = cos (90 -θ)


So sin 20° = cos (90 – 20)


∴ sin 20° = cos 70°


ii. We know that,


Let the unknown angle beθ


tan 30° = 1/√3


tanθ = 1/tan 30°


=


tanθ = √3


θ = tan-1(√3)


∴θ = 60°


iii. We know that,


cosθ = sin (90 -θ )


cos 40° = sin (90 – 40)


∴ cos 40° = sin 60°


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