Sine & Cosine for Obtuse Angles
Maths: Edexcel IGCSE Higher, topic 4.6.3
Sine Between 90° and 180°
Sine and cosine can be used for angles beyond 90°. You need to know how these functions behave beyond 90°.
Sine graph
- The graph for sine at different angles can be seen above.
- Sine is a periodic function that repeats every 360°.
Sine between 90° and 180°
- Sine has a value of +1 at sin(90°)
- Sine has a value of 0 at sin(180°)
- The value of sine is always positive between 90° and 180°.
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Values of sine
- You need to learn the key values of sine between 90° and 180°. You'll find these values above.
Cosine Between 90° and 180°
Cosine can be used for angles beyond 90°. You need to know how these functions behave beyond 90°.
Cosine graph
- The graph for cosine at different angles can be seen above.
- Cosine is a periodic function that repeats every 360°.
Sine between 90° and 180°
- Cosine has a value of 0 at cos(90°)
- Cosine has a value of −1 at sin(180°)
- The value of cosine is always negative between 90° and 180°.
Values of cosine
- You need to learn the key values of cosine between 90° and 180°. You'll find these values above.
Test yourself on Sine & Cosine for Obtuse Angles
How often does the graph for sine repeat?
What is the value of sin(90°)?
What is the value of sin(120°)?
What is the value of sin(135°)?
What is the value of sin(150°)?