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Lesson 1: Trigonometric Functions of Acute Angles. Done by: Justin Lo Lee Bing Qian Danyon Low Tan Jing Ling. Trigonometric Functions. The three main functions in trigonometry are Sine , Cosine and Tangent . They are often shortened to sin , cos and tan.
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Lesson 1:Trigonometric Functions of Acute Angles Done by: Justin Lo Lee Bing Qian Danyon Low Tan Jing Ling
Trigonometric Functions • The three main functions in trigonometry are Sine, Cosine and Tangent. • They are often shortened to sin, cos and tan.
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Sin, Cos, Tan A Hypotenuse Let this angle be x Opposite C B Adjacent
A Hypotenuse Let this angle be x Opposite SOH CAH TOA • "Opposite" is opposite to the angle x • "Adjacent" is adjacent (next to) to the angle x • "Hypotenuse" is the longest line C B Adjacent
Example 1: Find sin Line B (Hypotenuse) = 2 cm Line C = 1 cm Line C is opposite to angle Solution: Recall the formula: S Line A = cm Length of Line C (Opposite) Length of Line B (Hypotenuse)
Example 2: Find Line B (Hypotenuse) = 2 cm Line C = 1 cm Line C is adjacent to angle Solution: Recall the formula: Line A = cm Length of Line C (Adjacent) Length of Line B (Hypotenuse)
Example 3: Line B (Hypotenuse) = cm Find Line C = 1 cm Solution: Line A = 1 cm Recall the formula: Length of Line A/C (Opposite) Length of Line C/A (Adjacent)
A B C
Note: • Always draw a diagram to visualise if confused! • What if the triangle is not right-angled? Can we still use sin, cos, tan? • Angle of reference • Applies to adjacent and opposite too • Dependent on angle not triangle
Think… • How far up a wall could Bob the Builder reach with a 30 foot ladder, if the ladder makes a 70° angle with the ground? (2d.p) 0.93969= y= 28.19 30 y
Inverse Trigonometric Functions • Just as the square root function is defined such that y2 = x, the function y = arcsin(x) is defined so that sin(y) = x
Example 4: Find 5 cm x 3 cm Solution: Answer Recall the formula: 4cm
Example 5: Find 13 cm x 5 cm Solution: Answer Recall the formula: 12cm
Example 6: Find 13 cm x 5 cm Solution: Answer Recall the formula: tan 12cm