diff --git a/src/core/function.js b/src/core/function.js
index 0fca3e627..acce24feb 100644
--- a/src/core/function.js
+++ b/src/core/function.js
@@ -628,8 +628,13 @@ class PostScriptEvaluator {
           }
           break;
         case "atan":
+          b = stack.pop();
           a = stack.pop();
-          stack.push(Math.atan(a));
+          a = (Math.atan2(a, b) / Math.PI) * 180;
+          if (a < 0) {
+            a += 360;
+          }
+          stack.push(a);
           break;
         case "bitshift":
           b = stack.pop();
@@ -650,7 +655,7 @@ class PostScriptEvaluator {
           break;
         case "cos":
           a = stack.pop();
-          stack.push(Math.cos(a));
+          stack.push(Math.cos(((a % 360) / 180) * Math.PI));
           break;
         case "cvi":
           a = stack.pop() | 0;
@@ -774,7 +779,7 @@ class PostScriptEvaluator {
           break;
         case "sin":
           a = stack.pop();
-          stack.push(Math.sin(a));
+          stack.push(Math.sin(((a % 360) / 180) * Math.PI));
           break;
         case "sqrt":
           a = stack.pop();
diff --git a/test/pdfs/.gitignore b/test/pdfs/.gitignore
index 1c6e6b325..55c567aee 100644
--- a/test/pdfs/.gitignore
+++ b/test/pdfs/.gitignore
@@ -273,6 +273,7 @@
 !issue13316_reduced.pdf
 !issue15977_reduced.pdf
 !issue4575.pdf
+!colorspace_atan.pdf
 !bug1011159.pdf
 !issue5734.pdf
 !issue4875.pdf
@@ -294,6 +295,7 @@
 !find_all.pdf
 !helloworld-bad.pdf
 !zerowidthline.pdf
+!colorspace_cos.pdf
 !issue13242.pdf
 !js-colors.pdf
 !annotation-line-without-appearance-empty-Rect.pdf
@@ -423,6 +425,7 @@
 !issue5475.pdf
 !issue10519_reduced.pdf
 !annotation-border-styles.pdf
+!colorspace_sin.pdf
 !IdentityToUnicodeMap_charCodeOf.pdf
 !PDFJS-9279-reduced.pdf
 !issue5481.pdf
diff --git a/test/pdfs/colorspace_atan.pdf b/test/pdfs/colorspace_atan.pdf
new file mode 100644
index 000000000..897495b8f
Binary files /dev/null and b/test/pdfs/colorspace_atan.pdf differ
diff --git a/test/pdfs/colorspace_cos.pdf b/test/pdfs/colorspace_cos.pdf
new file mode 100644
index 000000000..08cd1fb72
Binary files /dev/null and b/test/pdfs/colorspace_cos.pdf differ
diff --git a/test/pdfs/colorspace_sin.pdf b/test/pdfs/colorspace_sin.pdf
new file mode 100644
index 000000000..5b56008d3
Binary files /dev/null and b/test/pdfs/colorspace_sin.pdf differ
diff --git a/test/test_manifest.json b/test/test_manifest.json
index f3ffc1ecc..62552aabe 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -840,6 +840,12 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "colorspace_sin",
+       "file": "pdfs/colorspace_sin.pdf",
+       "md5": "4e341c346f4f37cd94b82c532badb8fd",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "issue215",
        "file": "pdfs/issue215.pdf",
        "md5": "31f3dc60ecf008987d970edfd2b1df61",
@@ -2420,6 +2426,12 @@
        "rounds": 1,
        "type": "eq"
     },
+    {  "id": "colorspace_cos",
+       "file": "pdfs/colorspace_cos.pdf",
+       "md5": "d3703784c2558f33e03b91dccb745b6c",
+       "rounds": 1,
+       "type": "eq"
+    },
     {  "id": "issue6692",
        "file": "pdfs/issue6692.pdf",
        "md5": "ba078e0ddd59cda4b6c51ea10599f49a",
@@ -3837,6 +3849,12 @@
       "rounds": 1,
       "type": "eq"
     },
+    {  "id": "colorspace_atan",
+       "file": "pdfs/colorspace_atan.pdf",
+       "md5": "ec310d65a1849a39ae57d0d16b17261d",
+       "rounds": 1,
+       "type": "eq"
+    },
     {
       "id": "bug1199237",
       "file": "pdfs/bug1199237.pdf",
diff --git a/test/unit/function_spec.js b/test/unit/function_spec.js
index 1791bf911..3e167054a 100644
--- a/test/unit/function_spec.js
+++ b/test/unit/function_spec.js
@@ -138,9 +138,9 @@ describe("function", function () {
       const expectedStack = [254 & 1];
       expect(stack).toEqual(expectedStack);
     });
-    it("calculates the inverse tangent of a number", function () {
-      const stack = evaluate("{ 90 atan }");
-      const expectedStack = [Math.atan(90)];
+    it("the angle in degrees (0-360) whose tangent is num/den.", function () {
+      const stack = evaluate("{ 1 -1 atan }");
+      const expectedStack = [135];
       expect(stack).toEqual(expectedStack);
     });
     it("handles bitshifting ", function () {
@@ -158,9 +158,9 @@ describe("function", function () {
       const expectedStack = [99, 98, 99, 98];
       expect(stack).toEqual(expectedStack);
     });
-    it("calculates the cosine of a number", function () {
-      const stack = evaluate("{ 90 cos }");
-      const expectedStack = [Math.cos(90)];
+    it("calculates the cosine of an angle in degrees", function () {
+      const stack = evaluate("{ 180 cos }");
+      const expectedStack = [-1];
       expect(stack).toEqual(expectedStack);
     });
     it("converts to int", function () {
@@ -358,9 +358,9 @@ describe("function", function () {
       const expectedStack = [10];
       expect(stack).toEqual(expectedStack);
     });
-    it("calculates the sine of a number", function () {
+    it("calculates the sine of an angle in degrees", function () {
       const stack = evaluate("{ 90 sin }");
-      const expectedStack = [Math.sin(90)];
+      const expectedStack = [1];
       expect(stack).toEqual(expectedStack);
     });
     it("calculates a square root (integer)", function () {