Sine and cosine rules and area of a triangle Quiz

1. What is the exact value of $\sin150^\circ$?

• A. $-\frac12$
• B. $\frac{\sqrt3}{2}$
• C. $\frac12$
• D. $-\frac{\sqrt3}{2}$

2. What is the exact value of $\cos120^\circ$?

• A. $-\frac12$
• B. $\frac12$
• C. $-\frac{\sqrt3}{2}$
• D. $\frac{\sqrt3}{2}$

3. In triangle $ABC$, $a=8$, $A=30^\circ$ and $B=45^\circ$. Find $b$.

• A. $4\sqrt2$
• B. $8\sqrt2$
• C. $8$
• D. $16$

4. A triangle has sides $5$, $7$ and $8$. Find the cosine of its largest angle.

• A. $\frac{5}{7}$
• B. $-\frac17$
• C. $\frac{3}{5}$
• D. $\frac17$

5. Find the area of a triangle with sides $10$ and $12$ and included angle $30^\circ$.

• A. $30$
• B. $60$
• C. $30\sqrt3$
• D. $60\sqrt3$