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Question

If θ lies in the first quadrant and \(\cot \theta = \frac{{63}}{{16}}\) , then what is the value of (sin θ + cos θ)?

This question was previously asked in
CDS I 2020 Elementary Mathematics Previous Year Paper (02-Feb-2020)
The correct answer is \(\frac{{79}}{{65}}\)

Given:

\(\cot θ = \frac{{63}}{{16}}\)

Formula Used:

sin θ = Perpendicular/Hypotenus

cos θ = Base/ Hypotenuse

cot θ = Perpenicular/Base

Pythagorus theorem

(Hypotenus) 2= (Perpendicular) 2+ (Base) 2

Calculation:

\(\cot θ = \frac{{63}}{{16}}\)  = B/P

Here, hypotenuse =  \(\sqrt {{{63}^2} + {{16}^2}} = \sqrt {4225} \)  = 65

So,

sinθ = P/H = 16/65

cosθ = B/H = 63/65

∴ (sin θ + cos θ) = (16/65) + (63/65) = 79/65
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