If SEC A=13/12 Calculate Sin A and Cot A. (A is an acute angle.) | Bzziii.com
If sec A=`13/12`, calculate sin A and cot A. (A is an acute angle.)
Finding cos θ
cos θ = `"1"/"sec θ "`
cos θ = `\frac{1}{\frac{13}{12}}`
cos θ = `\frac{12} {13}`
`"Side adjacent to ∠θ "/"Hypotenuse"` = `\frac{12} {13}`
`"AB"/"BC"` = `12/13`
Let, AB = 12x
& AC = 13x
Using Pythagoras theorem to find BC
`"(Hypotenuse)"^2` = `"(Height)"^2` + `"(Base)"^2`
`"AC"^2` = `"AB"^2` + `"BC"^2`
`"(13x)"^2` = `"(12x)"^2` + `"(BC)"^2`
`"(BC)"^2` = `"(13x)"^2` - `"(12x)"^2`
`"(BC)"^2` = 169`"x"^2` - 144`"x"^2`
`"(BC)"^2` = 25`"x"^2`
BC = `\sqrt{25"x"^{2}}`
BC = `\sqrt{5^2x^{2}}`
BC = 5x
Now, sin θ = `"BC"/"AC"`
= `"5x"/"13x"`
= `"5"/"13"`
cos θ = `"12"/"13"`
tan θ = `"BC"/"AB"`
= `"5x"/"12x"`
= `"5"/"12"`
cot θ = `"1"/"tan θ "`
= `\frac{1}{\frac{5}{12}}`
= `12/5`
Thus, sin θ = `"5"/"13"` and cot θ = `"12"/"5"`
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