in the triangle abc angle b 90 and a 38 given, Ratio And Percentage, Mathematics (O-Level)

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Question:In the triangle ABC, the angle B=`90^@` and the angle A=`38^@`, Given that BC=4 cm, calculate the Length of AB.

Answer The tangent of the angle A=`(BC)/(AB)` . The unknown side is the denominator of the fraction. Therefore consider the angle C.
The angle C = `90^@` - `38^@` = `52^@`
                                 `:. tan 52^@ = (AB)/4`
`:.` 4 tan `52^@` cm = `4 xx 1.2799 cm`
                                    = 5.1196 cm
                                    = 5.12 cm (correct to 3 sig. fig.).

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In the triangle ABC, the angle B=`90^@` and the angle A=`38^@`, Given that BC=4 cm, calculate the Length of AB.

Question:In the triangle ABC, the angle B=`90^@` and the angle A=`38^@`, Given that BC=4 cm, calculate the Length of AB.

Answer The tangent of the angle A=`(BC)/(AB)` . The unknown side is the denominator of the fraction. Therefore consider the angle C. The angle C = `90^@` - `38^@` = `52^@` `:. tan 52^@ = (AB)/4` `:.` 4 tan `52^@` cm = `4 xx 1.2799 cm` = 5.1196 cm = 5.12 cm (correct to 3 sig. fig.).