Paper 22 Q21IGCSE 0580 May/June 2023

Question

21 Solve the equation 5sinx=-3 for 0°⩽x⩽360°.

This question tests your ability to solve trigonometric equations using inverse trigonometric functions and understanding of the sine function's behaviour over a full 360° cycle. You need to find all possible angles where the sine value equals -3/5.

Step-by-Step Solution

Key Takeaway

When solving trigonometric equations with negative values, always check which quadrants give negative results and find both solutions within the given range.

Common Mistakes

Only finding one solution instead of checking all quadrants where sine is negative
Using the negative angle from the calculator (-36.87°) directly instead of finding the correct quadrant angles
Forgetting to convert the decimal form -3/5 = -0.6 before using the calculator

Exam Tip

Always sketch a quick CAST diagram or remember 'All Students Take Chemistry' to identify which quadrants give negative sine values, then systematically find all solutions in the given range.

Need More Help With Equations?

Try our AI maths tutor for instant, personalised help, or take the diagnostic quiz to find all your knowledge gaps.

Ask the AI Tutor Take Diagnostic Quiz

Learn more about this topic: Equations →