LEARN · EXPLAIN · REVISE

Find the triangle area.

Read the idea, work independently, then explain what changed.

TOPIC 01

Plane vectors and applications: mixed assessment

A mixed assessment: identify the method, justify it and revise your reasoning.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Standard#Your turn

a=18,\quad b=3,\quad C=30^{\circ}

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Translate the geometry or physical quantity into vectors and check angle conventions.

Hint 2

Use half the product of two sides and sine of their included angle.

Worked solution

Translate the geometry or physical quantity into vectors and check angle conventions.
Calculate or simplify this relation.
$S=\frac12ab\sin C=\frac12(18)(3)(1/2)=13.5$
The angle must be the included angle, not an arbitrary triangle angle.

The requested value is 13.5.

Checks and common pitfalls: The angle must be the included angle, not an arbitrary triangle angle.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment